
Class I K*S| 

Book 

CojpghtN 

GQRERIGHT DEPOSIT 



" The vital knowledge — that by which we 
have grown as a nation to what we are, and 
which now underlies our whole existence, is a 
knowledge that has got itself taught in nooks 
and corners ; while the ordained agencies /or 
teaching have been mumbling little else but 
dead fot mulas. ,} 

i( That which our school courses leave almost 
entirely out, we thus find to be that which most 
nearly concerns the business of life. All our 
industries would cease, were it not for that in- 
formation which men begin to acquire as they 
best may after their education is said to be 
finished. A nd were it not for this information, 
that has been from age to age accumulated and 
spread by unofficial means, these industries 
would never have existed." — Herbert Spencer. 



COPYRIGHTED, 1896, 

BY 

THEO. AUDEL & CO. 




Press of L. Middled itch Co. 



EL.ECTROTYPED BY STODDER BROS. 



NEW 

Ail 



CATECHISM ^ 

OF 

ELECTRICITY, 

A Practical Treatise, 




AWKINS, M. E., 



Author of Hand Book of Calculations for Engineers ; Maxims 

and Instructions for the Boiler Room ; Aids to Engineers' 

Examinations with Questions and Answers ; Steam 

Engineering Miscellany, Etc., Etc. 




*«U\ 



-^ 



v 



Relating to The Dynamo and Motor ; Wiring ; The 
Electric Railway ; Electric Bell Fitting ; Electric 
Lamps ; Electric Elevators ; Electric Lighting; 
Electro Plating ; The Telegraph and Tele- 
phone ; Electric Elevator, Tables 
and Measurements. 



THEO. AUDEL & COMPANY, Publishers, 

63 Fifth Avenue, Cor. 13th Street, New York. 
1896. 




THOS. A EDISON 






This work is respectfully dedicated to 

THOMAS A. EDISON, 

of Llewellyn Tark, N. J. 



" From possibilities 
to realities." 



PREFACE. 



What can the autnor of this treatise say in sending 
it forth to be added to the much more extensive 
works already published relating to the same subject. 
He can say this. 

There are a thousand spoken languages in the 
world, each mode of speech is more or less perfect, 
and easily understood. 

But, outside those born to a particular tribe or 
nation, al) other tongues save their own are a babel 
of sound — a literal gibberish. 

Thus, the Chinaman cannot understand the 
Italian, nor the Frenchman the German, and so on 
through the hundreds of dialects; a man who knows 
six languages is rare, although Elihu Burritt the 
learned blacksmith was said to be familiar with 
forty or more. 

It is the same with the writing of books ; each author 
must use his own native " lingo " addressed to those 
born to the same tribe as himself. 



xii Preface, 

Now, for many years, a large number of the patrons 
of the author's other books have signified a desire 
for him to write a work on Electricity, and the time 
being ripe, he now sends it forth addressed (only) 
to those familiar with a common language and 
animated by a common tie of association and life 
with himself. 

Hence, this work is addressed; not to the exper- 
imenter or to the toy-maker, nor to the scholar in 
school or college, but to those who have to deal with 
Electricity as a part of their life work ; to those who 
hold it in check, like a powerful horse and render 
serviceable this mysterious force — the rein to hold 
and guide it is knowledge. 

Back of the desire for a considerable circulation 
of the printed book lies the earnest wish that it may 
be thoroughly useful to that class of men who must 
perforce use electricity as their bondsman or serve it 
as an inexorable master. 

And this is the true office of a book relating to the 
arts or sciences ; to explain the unvarying laws upon 
which all true progress is based; to classify and 
arrange for ready reference this information so that 
it may be readily available; to furnish hints and 
suggestions leading to further and thorough re- 
search in all lines leading from the subjects discussed ; 
in short to reduce the every-day practice of a 
thousand skilled workers to an unvarying science; 
science being defined as the "orderly arrangement 
of knowledge." 



Preface. xiii 

It is also the heartfelt wish of the author that this 
work may be found to be an introduction of the 
reader and student to a wide acquaintance with what 
may be termed electrical literature. 

In a science which has occupied the whole of very 
many lives in the investigation of its laws and an 
immense expenditure of money in experimental tests, 
it were vain to expect from a single book much 
more than a limited view of some one part of the 
subject, or better yet, a work giving the clue to 
further research and study in many directions. 

So, in this work the author trusts the student will 
at least find " the end of the rope " which drawn out 
will make him master of the principles and practice 
relating to practical Electricity. And, in the abridge- 
ment and selection of the ever-widening subject- 
matter, so present it, that it can at the pleasure or 
profit of the student, be run out to infinitude in any 
useful direction. 

With these few introductory words and added good 
wishes for the progress and prosperity of the reader, 
the author thus apologizes (for a preface is usually 
an apology) for issuing a New Catechism of Electri- 
city. 



Introduction. 



INTRODUCTION. 




HE great forces of the world are 
invisible and impalpable ; we 
cannot grasp or handle them ; 
and though they are real enough 
they have the appearance of 
being very unreal. Electricity 
and Gravity are as subtle as they 
are mighty ; they elude the eye and hand of the most skillful 
philosopher. In view of this, it is well for the average man 
not to try to fathom, too deeply, the science of either ; neither 
Edison or Tesla have done that yet. 

To take the machines and appliances as they are " on the 
market," and to acquire the skill to operate them, is the long- 
est step toward the reason for doing it, and why the desired 
results follow— thus working on the natural method of judg- 
ing causes from effects. 

The history of the development of " Practical Electrics" 
does not cover many years. Not a few -people can easily re- 
member all the progressive steps from a humble beginning to 
the time, now, when it has become the leading study of the 
scientific and engineering world. 



Introduction. 



Although electricity was known to the ancient Greeks the 
uses to which it might be applied have remained unknown for 
thousands of years. It was reserved for Franklin, Volta, Am- 
pere, Ohm, and Farraday, with a few others, to discover the 
laws which govern it. The development of the science in its 
application to the needs of human life may be considered to 
date from the time of Farraday, whose career ended in 1867, 
after a long and brilliant career spent in scientific research. 

The time has gone by when in answer to the question, 
" What is Electricity," it can be truly said " It is not known," 
for as much is now known of its nature an \ source as of the 
nature and source of Gravity, Heat, Chemical affinity, etc. 
The following ' ' definitions ' ' carefully written by men high- 
est in authority, are both interesting and instructive. 

" There are certain bodies which when warm and dry, ac- 
quire by friction, the property of attracting feathers, fila- 
ments of silk or indeed, any light body toward them. This 
property is called Electricity, and bodies which possess it are 
said to be electrified." (Linnaeus Cumming.) 

" The theory of Electricity adopted throughout these les- 
sons is, that Electricity, whatever its true nature, is one not 
two; that this Electricity, whatever it may prove to be, is not 
matter and is not energy ; that it resembles both matter and 
energy in one respect, however, in that it cannot be created 
nor destroyed. ' ' (Sylvanus P. Thompson). 



Note.— When Benjamin Franklin made his discovery of the identity 
of lightning and electricity, people asked: " Of what use is it?" The 
philosopher's retort was : 4 4 What is the use of a child ? It may become 
a man !" 



Introduction. xvii 



" Whatever Electricity is, it is impossible to say, but for 
the present it is convenient to look upon it as a kind of invis- 
ible something which pervades all bodies.' ' (W. Perrin 
Maycock). 

"There is nothing more certain to-day than that Electricity 
is not a fluid. " (Prof. Rowland). 

' * Throughout the nineteenth century this enigma (What is 
electricity?) has been the object of numerous researches * 
* * and yet the inner working of electrical phenomena re- 
mains still a deeper mystery." (A. Stoletow.) 

These quotations express all that science can give us in a 
time when there are published every month in the English, 
French and German languages over 150 issues of periodicals 
devoted exclusively to electrical subjects, besides which there 
are probably twice as many more journals devoted to other 
branches of science and engineering which sometimes have 
articles on electrical subjects. 

In 1867 an English mathematician, Maxwell, proved math- 
ematically that light and electricity were the same. In 1888 
Heinrich Hertz proved by experiment that this was true, 
and the "pointings" of very recent investigations rather 
confirm the theory that they are one and the same. 



Note. — One of the dreams of the modern scientist is the direct trans- 
formation of the radient energy of the sun into electric energy. To what 
extent this is possible is considered by a well-known electrical writer, who 
says : " It is a well-known principle in physics that in the last analysis all 
the forces of Nature are derived from the sun. There are the calorific and 
luminous vibrations of the sun, which, imprisoned in the coal strata and 
in combustible vegetation, afford the means of producing steam. When 
one reflects upon the tendency to utilize these forces in the form of elec- 
tricity, a problem of first importance is to transfer the solar energy di- 
rectly into electric energy without the agency of any intermediary." 



xviii Introduction. 



Very much the same way in which electricity is concen- 
trated by the action of the dynamo, so has the sunlight been 
"concentrated" by a powerful sun glass constructed in 
France, made under the supervision of the savant, M. de 
Villette. This glass generated heat sufficient to melt a cop- 
per coin of the size of our silver 25-cent piece in seven and a 
half seconds. George Parker, of Fleet street, London, made 
a glass more powerful ; it was three feet in diameter and 
so powerful that it was actually m used to melt substances 
which were too refractory for the furnaces. The best authori- 
ties on heat say that it had a power of 166.362 degrees Fahr. 
This is best understood when it is known that it only takes a 
temperature of 2,787 degrees to melt cast iron so that it will 
flow like water. 

It is from those engineers and electricians who are in daily 
contact with electrical appliances that we are most likely to 
get the true definition of the subject. They say boldly and 
to the point, " Electricity is electricity," and motormen are 
frequently in the habit of describing the electric-current 
which drives their trolley-car, as "the juice." " Let on the 
juice ! " or, "Shut off the juice ! " this being always intelli- 
gable to the most scientific as well as the most illiterate. 

The competent engineer to-day is expected to combine a 
practical knowledge of the engine and dynamo room with a 
proportionate information to be gained only by schools, books 
and professional instruction, intended to qualify him to oper- 
ate and manage economically and intelligently, electrical ma- 
chines ; to install electrical plants ; to perform calculations 
involving electrical units and to locate and remedy faults in 
electrical machines in general. 



Introduction. 



Not only the competent engineer, but everybody needs to 
acquire as much information as possible of this universal prop- 
erty of nature now brought into such close connection with 
the everyday life of modern civilization. It is the aim of this 
publication to so present the subject that it may be of wide 
and useful assistance to the student. 

Quite recently a distinguished professor of Harvard Univer- 
sity published an article in which he grouped the engineers 
now working side by side for the development of our material 
resources into three classas. First, those men, many of them 
eminent in the profession, who are the product of the work- 
shop ; whose experience and education have been obtained 
entirely in the field or workshop, and from a few available 
books. 

Second. Men who have graduated from literary or natural 
science departments of colleges and have learned engineering 
after leaving their classes — drawn to it by a strong taste for 
the profession or by the pressure of circumstances. 

Third, the younger men, graduated from schools avowedly 
technical or from the technical departments of universities. 
These men are gradually supplanting the other two classes, as 
the demand for greater attainment and better education in- 
creases, and as competition and the invention of labor saving 
machinery turns the mechanic into a laborer, and raises the 
status of the educated engineer. 

The next generation, the professor believes, will see the 
men with only workshop or academic training practically cut 
off from the profession of engineering. 



Introduction. 



Happily for the class for whom this work is compiled there 
is another side to the argument which might show that the 
men most handicapped in the race for supremacy is the 
graduate alluded to in class three, for to quote the same 
kindly author, only, ' ' Occasionally our schools develop a 
man whose talent and capacity for work will enable him to 
study and to retain the higher branches of mathematics and 
physics, and at the same time to grasp their practical applica- 
tion to the need of modern life." 

This practically in the end leaves the field for the self- 
taught, resolute workers, who with one hand execute and the 
other gather in and assimilate from all sources the scientific 
or classified knowledge necessary for the best results, eco- 
nomical, executive and lasting. 




"Electricity has shown itself capable of in- 
finite service^ and its field is daily widening. 
It can bear thought on its rhythmic wings 
around the globe; carry the human voice 
hundreds of miles ; deliver messages on board 
moving trains ; flash into dazzling splendors 
along city thoroughfares ; light the abyss of 
the ocean ; operate countless automatic devices; 
warm us when cold ; fan us when heated, 
and treasure up and repeat all sounds and 
harmonies. At the summons of inventive 
genius it has outwrought the dreams of 
magic.''' 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICITY. 



While the nature and source of electricity still 
remains a mystery, and a constant challenge to the 
philosopher and engineer, many things about it 
have become positively known — thus — it is posi- 
tively assured that electricity never manifests itself 
except when there is some mechanical disturbance 
in ordinary matter, and every exhibition of elec- 
tricity in any of its multitudinous ways may always 
be traced back to a mass of matter. 



Electricity, it is also conceded, is without weight, 
and, while electricity is without doubt, one and the 
same, it is for convenience sometimes classified 
according to its motion, as 

1. Static Electricity, or electricity at rest. 

2. Current Electricity, or electricity in motion. 

3. riagnetism, or electricity in rotation. 

4. Electricity in vibration (Radiation). 



Note.— Electricity is a name derived from the Greek 
word Electron— amber. It was discovered more than 2,000 
years ago that amber when rubbed possessed the curious 
property of attracting light bodies. It was discovered after- 
wards that this property could be produced in jet by friction, 
and in A. D. 1600 or thereabouts, that glass, sealing-wax, 
etc., were also affected by rubbing, producing electricity. 



NEW CATECHISM OF ELECTRICITY. 23 

Other useful divisions are into 
i. Positive and 

2. Negative Electricity. 
And into 

I . Static, as the opposite of 

2. Dynamic Electricity. 

There are still other definitions or divisions which are in 
every-day use, such as " Frictional electricity," "Atmospheric 
electricity," "resinous electricity," "vitreous electricity," 
"photo-electricity," etc., etc. 

While it is almost certain that, broadly, magnetism and 
electricity are one, in practice it is a necessity to use these 
divisions to explain the various conditions and uses to which 
they are put and in which they exist. 

USEFUL DEFINITIONS RELATING TO ELECTRICITY. 

Static Electricity. This is a term employed to define 
electricity produced by friction. It is properly employed in 
the sense of a static charge which shows itself by the attrac- 
tion or repulsion between charged bodies. When static 
electricity is discharged, it causes more or less of a current, 
which shows itself by the passage of sparks or a brush dis- 
charge; by a peculiar prickling sensation; by a peculiar smell 
due to its chemical effects ; by heating the air or other sub- 
stances in its path ; and sometimes in other ways. 



Note.— Statics is that branch of mechanics which treats of the forces 
that keep bodies at rest or in equilibrium. Dyuamics treats of bodies 
in motion. Hence static- electricity is electricity at rest. The earth's great 
store of electricity is at rest or in equilibrium. 

That branch of the science which treats of the laws of electricity resid- 
ing on the surface of bodies, as a charge, is termed electrostatics. 



24 NEW CATECHISM OF ELECTRICITY. 



Current electricity. This may be defined as the quantity 
of electricity which passes through a conductor in a given 
time — or, electricity in the act of being discharged, or elec- 
tricity in motion. 

An electric current manifests itself by heating the wire or 
conductor, by causing a magnetic field around the conductor 
and by causing chemical changes in a liquid through which 
it may pass. 

Radiated electricity is electricity in vibration. Where the 
current oscillates or vibrates back and forth with extreme 
rapidity, it takes the form of waves which are similar to waves 
of light. 

Positive electricity. This term expresses the condition of 
the point of an electrified body having the higher energy 
from which it flows to a lower level. The sign which denotes 
this phase of electric excitement is -f- ; all electricity is either 
positive or, — , negative. 

Negative electricity. This is the reverse condition to the 
above and is expressed by the sign or symbol — . These two 
terms are used in the same sense as hot and cold. 



In 1749, Benjamin Franklin observing lightning to possess almost all 
the properties observable in electric sparks, suggested that the electric 
action of points, which was discovered by him, might be tried on thunder- 
clouds, and so draw from them a charge of electricity. He proposed, 
therefore, to fix a pointed iron rod to a high tower, but shortly after suc- 
ceeded in another way. He sent up a kite during the passing of a storm, 
and found the wetted string to conduct electricity to the earth, and to 
yield abundance of sparks. These he drew from a key tied to the string, 
a silk ribbon being interposed between his hand and the key for safety. 
Iyeyden jars could be charged, and all other electrical effects prcduced, by 
the sparks furnished from the clouds. The proof of the identity was 
complete. The kite experiment was repeated by Romas, who drew from 
a metallic string sparks 9 feet long. In 1753, Richmann, of St. Petersburg, 
who was experimenting with a similar apparatus, was struck by a sudden 
discharge and killed. 



NEW CATECHISM OF ELECTRICITY. 25 

Atmospheric electricity is the free electricity of the air 
which is almost always present in the atmosphere. Its exact 
cause is unknown. 

The phenomena of atmospheric electricity are of two kinds; 
there are the well-known manifestations of thunderstorms ; 
and there are the phenomena of continual slight electrification 
in the air, best observed when the weather is fine ; the Aurora 
constitute a third branch of the subject. 

Dynamic electricity. This term is used to define current 
electricity to distinguish it from static electricity. This is the 
electricity produced by the Dynamo. 

Frictional electricity is that produced by the friction of 
one substance against another. 

Resinous electricity. This is a term formerly used, in 
place of negative electricity. The phrase originated in the 
well known fact that a certain (negative) kind of electricity 
was produced by rubbing rosin. 

Vitreous electricity is a term, formerly used, to describe 
that kind of electricity (positive) produced by rubbing glass. 

Magneto ^electricity is electricity in the form of currents 
flowing along wires ; it is electricity derived from the motion 
of magnets — hence the name. 

Voltaic electricity. This is electricity produced by the 
action of the voltaic cell or battery. 

Electricity itself is the same thing, or phase of energy 
by whatever source it is produced and the foregoing definitions 
are only given as a matter of convenience to aid in its daily 
application to the service of man. 



26 NEW CATECHISM OF ELECTRICITY. 

Early Experiments in Electricity. 

" A shock was in this manner sent through a regiment of 
soldiers. At an early period in the progress of electrical dis- 
covery, M. Nollet transmitted a discharge through a series of 
1 80 men ; and at the convent of Carthusians a chain of men 
being formed extending to the length of 5,400 feet, by means 
of metalic wires extended between every two persons compos- 
ing it, the whole series of persons was affected by the shock 
at the same instant. 

Experiments on the transmission of the shock were made 
in lyondon by Dr. Watson, in the presence of the Council of the 
Royal Society, when a circuit was formed by a wire carried from 
one side of the Thames to the other over Westminster Bridge. 

One extremity of this wire communicated with the interior 
of a charged jar, the other was held by a person on the oppo- 
site bank of the river. This person held in his other hand an 
iron rod, which he dipped in the river. On the other side 
near the jar stood another person, holding in one hand a wire 
communicating with the exterier coating of the jar, and in 
the other hand an iron rod, This rod he dipped in the river 
when instantly the shock was received by both persons, the 
electric fluid having passed over the bridge, through the body 
of the person on the other side, through the water across the 
river, through the rod held by the other person, and through 
his body to the exterior coating of the jar. 

Familiar as such a fact may now appear, it is impossible to 
convey an adequate idea of the amazement bordering on 
incredulity with which it was at that time witnessed." 



NEW CATECHISM OF ELECTRICITY. 



27 



MAGNETISM AND MAGNETS. 




,4 



■;\ 



v?.':'^$& 



5* ... «W.3e.' 

"- - - 



Magnetism is that branch of 
f >, \ science which treats of the na- 

ture and properties of magnets 
?■■:: and magnetic fields. 

g.v The theory proposed to ac- 

|g count for the magnetization of 
g| iron is as follows : Each little 
£v? particle of iron is supposed to 
Vji be, and to remain always mag- 
•;;.>! netic. In an un magnetized iron 
bar these molecular magnets 
are arranged irregularly. These little molecules resist being 
turned out of their usual positions. Hence when a mag- 
netizing force is brought to bear upon them, the first effect is 
to turn those little molecules round, whoses axes are already 



Fig. 10. 



Note. — The name magnet was given by the ancients to certain hard 
black stones found in various parts of the world, notably at Magnesia in 
Asia Minor, which possessed the property of attracting to them small 
pieces of iron or steel. This magic property, as they deemed it, made 
the magnet-stone famous; but it was not until the tenth or twelith century 
that such stones were discovered to have the still more remarkable prop- 
erty of pointing north and south when hung up by a thread. This prop- 
erty was turned to advantage in navigation, and from that time the 
magnet received the name of lodestone (or "leading-stone"). The 
natural magnet or lodestone is an ore of iron, known to mineralogists as 
magnetite. This ore is found in quantities in Sweden, Spain, Arkansas, 
the Isle of Elba and other parts of the world ; it frequently occurs in 
crystals, the usual form being the regular octahedron. 



28 NEW CATECHISM OF ELECTRICITY. 

MAGNETISM AND MAGNETS. 

most nearly in the direction of the magnetizing field. As the 
magnetizing force increases others are turned, increasing 
thereby the apparent magnetism ; at iast, all are turned with 
their poles in the direction of the magnetizing field. 

When this is the case, no further application of magnetiz- 
ing force, however great, can increase magnetization. This 
is the point of saturation. It is easily seen that shocks, or 
heating, or anything which loosens the molecules, tends to 
facilitate the acquirement of magnetization. On removing 
the magnetizing force, those molecules which have not been 
much strained out of their position, fall back to their old di- 
rections ; but those which have been greatly strained have 
acquired a permanent magnetic set, and hence remain. 

In the case of torsion or twisting of a wire, we have a 
similar behavior. A slight torsion within the limits of elas- 
ticity disappears when the twisting force is removed, but a 
violent torsion results in a permanent deformation, which 
does not disappear when the twisting force is removed. 

This theory explains how iron can remain, as it were, 
super-charged or super-saturated with temporary magnetism. 
In the iron there is very little resistance to magnetization ; 
that is to say, the molecules do not resist very strongly 
being turned in similar magnetic directions, and hence when 
the force is removed, there is very little restoring tendency 
to make them go back into irregular positions, but a little 
knock or twist imparts just the necessary disturbance, and 
causes the regularity to disappear, and with it the apparent 
magnetism. 



NEW CATECHISM OF ELECTRICITY. 2Q 

MAGNETISM AND MAGNETS. 

Magnetism is like electricity, it cannot be seen ; that it ex- 
ists is assured by certain effects which it produces. Toy 
magnets shaped like a horseshoe exhibit the principles upon 
which magnetism acts; i. e. y magnets attract and hold fast 
anything that is made of iron and steel, while they have no 
effect on brass, copper, zinc, gold or silver. 

A magnetized body cannot be regarded as a source of" 
energy in itself. Energy must be expended to magnetize the 
iron, and must also be expended to demagnetize it. 

Magnetism produces electricity as well as electricity pro- 
duces magnetism. 

During the application of the magnetizing force, any blows 
or shaking tend to facilitate the acquirement of magnetism, 
but when removed from the field, the same causes tend to re- 
move it. Heat operates in the same way. If a piece of steel 
is made red hot, then placed in a strong magnetic field and 
suddenly cooled, it acquires very strong permanent magnet- 
ism. Iron at a bright red heat is, however, not affected by a 
magnet. If a piece of iron, or better still, a piece of hard 
steel, be rubbed with a lodestone, it will be found to have also 
acquired the properties characteristic of the magnet ; it will 
attract light bits of iron and steel. 

This was all, or nearly all, that was known of the magnet 
until 1600, when Dr. Gilbert published a large number of 
magnetic discoveries in his famous work " De Magnete." 
He observed that the attractive power of a magnet appears 
to reside at two regions, and in a long-shaped magnet these 
regions, or poles, are usually at the ends. The portion of the 



30 NEW CATECHISM OF ELECTRICITY. 



MAGNETISM AND MAGNETS. 

magnet which lies between the two poles is apparently less 
magnetic, and does not attract iron filings so strongly ; and 
all round the magnet, halfway between the poles, there is no 
attraction at all. This region Gilbert called the equator of 
the magnet, and the imaginary line joining the poles he 
termed the axis. 

There is no insulator fcr magnetism. It penetrates every- 
thing known. The so-called protectors against magnetism 
are really only excellent conductors which form a short cut 
for the magnetism around the article to be protected. 

If a sheet of glass, or wood, or paper, be interposed between 
a magnet and the piece of iron or steel it is attracting, it will 
still attract it as if nothing were interposed. A magnet sealed 
up in a glass tube still acts as a magnet. Lucretious found a 
magnet put into a brass vase attracted iron filings through the 
brass. Gilbert surrounded a magnet by a ring of flames, and 
found it still to be subject to magnetic attraction from without. 
Across water, vacuum, and all known substances, the mag- 
netic forces will act; with the single exception, however, 
that magnetic force will not act across a screen of iron or 
other magnetic material. If a small magnet is suspended in- 
side a hollow ball made of iron, no outside magnet will affect 
it. A hollow shell of iron will therefore act as a magnetic 
cage, and screen the space inside it fro::i magnetic influences.. 

All magnetized sub3tances whether permanently or tempo- 
rarily magnetized have what is called polarity. The pole 
which tends to point northward when free to move is called 
the north pole. The other is the south pole. When two 



NEW CATECHISM OF ELECTRICITY. 31 

MAGNETISM AND MAGNETS. 

magnets are placed near to each other the N. pole of one is 
found to repel the N. pole and to attract the south pole of the 
other ; and the reverse. It is pre'cisely by this attraction and 
repulsion that motive power is produced by the agency of 
electricity. 

The magnetic field is the space around the magnet in which 
the compass needle or other detector of magnetism will be af- 
fected. The magnetic field is said to be comprised of lines of 
force. These are infinite in number, and gradually become 
weaker and weaker, until they disappear as the distance from 
the magnet is increased. 

The magnetic circuit is a closed circuit. The lines of force 
starting from the N. pole and entering again at the S. pole. 

Magnetic Flux. — This term indicates the number of lines 
that pass through the magnetic current. It has the same 
meaning as the term " magnetic flow." 

Magnetic Lag. — This is the tendency of hard iron and steel 
to take up magnetism slowly and part with it slowly. " Mag- 
netic retardation'' has the same meaning, also " magnetic 
inertia." 

Magnetic Saturation is the greatest magnetic force which 
can be permanently imparted to a steel bar. 

Residual Magnetism. — When a mass of iron has once been 
magnetized, it becomes a difficult matter to entirely remove 
all traces when the magnetizing agent has been removed, and, 
as a general rule, a small amount of magnetism is permanent- 
ly retained by the iron. The magnetism so retained by the 
iron is known as residual magnetism^ and it varies in amount 



NEW CATECHISM OF ELECTRICITY. 



MAGNETISM AND MAGNETS. 

with the quality of the iron. Well-annealed, pure, wrought- 
iron, as a rule, possesses very little residual magnetism, 
while, on the other hand, wrought-iron, which contains a 
large percentage of impurities, or which has been subjected to 
some hardening process, such as hammering, rolling, stamp- 
ing, etc., and cast-iron possesses a very large amount of resid- 
ual magnetism. This property of residual magnetism in iron 
is of great importance in the working of the self-exciting 
dynamo, and is, indeed, the essential principle of this class of 
machine. 

The Magnetic Field. — It is now understood that the phe- 
nomena of magnetism are due to an atmosphere of magnetic 
influence which surrounds the poles, and to a lesser, the whole 
of the magnet. This atmosphere is termed the magnetic field. 

Magnetic Tick. — When a bar of iron is suddenly magne- 
tized or demagnetized, it emits a slight sound, called the 
* ' page sound ' ' or the magnetic tick. 



Note.— If the North pole of a magnet is presented to the South pole 
of another magnet, they will attract and hold fast to each other; but, if 
a South pole is presentedto another South pole or a North pole to a North 
pole, they will repel each other, and there will be no attraction. 



NEW CATECHISM OF ELECTRICI'l Y. 33 

MAGNETISM AND MAGNETS. 

Strength of a Magnet. — The "strength " of a magnet is not 
the same thing as its " lifting power." The strength of a 
magnet is the strength of its poles. The strength of a 
magnet pole must be measured by the magnetic force which 
it exerts. 

The lifting power of a magnet depends both upon the form 
of the magnet and on its magnetic strength. A horse-shoe 
magnet will lift a load three or four times as great as a bar 
magnet of the same weight will lift. The lifting power is 
greater if the area of contact between the poles and the arma- 
ture is iucreased. Also the lifting power of a magnet grows 
in a very curious and unexplained way by gradually increasing 
the load on its armature, day by day until it bears a load which 
at the outset it could not have done. Nevertheless if the load 
is so increased that the armature is torn off, the power of the 
magnet falls at once to its original value. The attraction be- 
tween a powerful electro-magnet and its armature may 
amount to 200 lbs. per square inch. (See fig. 15, page 46.) 

Small magnets lift a greater load in proportion to their own 
weight than large ones. A good steel horse-shoe magnet 
weighing itself one pound ought to lift twenty pounds' weight. 
Sir Isaac Newton is said to have possessed a little lode. stone 
mounted in a signet ring which would lift a piece of iron 200 
times its own weight. 



34 NEW CATECHISM OF ELECTRICITY. 



USEFUL DEFINITIONS RELATING TO MAGNETS. 

Magnets made of steel are usually called permanent mag- 
nets ; these are of two forms, viz., the "bar magnet " and the 
" horseshoe magnet," which is merely the bar magnet turned 
around. 

Artificial Magnet. —Any magnet not found in nature is an 
artificial magnet. 

Horseshoe Magnet. — This is a magnetized bar of iron or 
steel bent in the form of a horseshoe or letter U. (See Fig. 10.) 

Natural Magnet is a name sometimes given to a lodestone. 
Natural magnets are usually of irregular form, although they 
are sometimes reduced to regular shapes by cutting and grind- 
ing. 

Compound Magnets consist of a number of single magnets 
separately magnetized, and afterwards bound together in bun- 
dles. Compound magnets are stronger in proportion to their 
weight than single magnets. 

Permaneut Magnet. — A magnet of hardened steel which 
retains its magnetism a long time after being magnetized. A 
permanent magnet will always attract and hold pieces of iron 
and steel. Its ends or poles are named North and South. 
There is usually a loose piece of steel or iron, called an 
"armature" put across the ends, which has the peculiar 
property of keeping the magnetism from becoming weaker. 

A Polarized Electro-Magnet is one whose core is a perman- 
ent magnet. Such magnets are used in Duplex Telegraphy. 
The armature of this magnet is released only by a current in 
a fixed direction. 



NEW CATECHISM OF ELECTRICITY. 



35 



ELECTRO MAGNETISM. 




Fig. 11. 

Klectro-magnetism is the foundation stone of commercial 
electricity. 

A magnet produced by passing! an electric current through 
a wire conductor coiled around a bar of soft iron is called an 
electro-magnet ; if the bar be of iron it will be a magnet 
only so long as the current flows, and electro magnetism is 
that science which relates to magnetism produced by the 
electric current, and which treats of the relation between 
electric currents and magnetism. 

In 1820 Oerstedt made the important discovery that a con- 
ductor through which a current of electricity is passing 
acquires thereby all the properties of a magnet. 



Note. — The great usefulness of the electro-magnet in its application 
to electric bells and telegraphic instruments lies in the fact that its mag' 
netism is under the control of the current ; when circuit is ' ' made " it be- 
comes a magnet, when circuit is " broken " it ceases to act as a magnet. 



36 



NEW CATECHISM OF ELECTRICITY. 



ELECTRO MAGNETISM. 

Almost immediately after Oerstedt's discovery, Arago and 
Davy independently discovered how to magnetize iron and 
steel by causing currents of electricity to circulate round 
them in spiral coils of wire. The method is shown in the 
simple diagram of Fig. n where a current from a single cell 
is passed through a spiral coil of wire, in the hollow of which 







Fig. 12. 



is placed a bar of iron or steel, which is thereby magnetized. 
The separate turns of the coil must not touch one another or 
the central bar, otherwise the current will take the shortest 
road open to it and will not traverse the whole of the coils. 
To prevent such short-circuiting by contact the wire of the 
coil should be overspun with silk or cotton, or covered with a 
layer of gutta-percha. 



NEW CATECHISM OF ELECTRICITY. 37 

ELECTRO MAGNETISM. 

All dynamic-electric machines are based upon that branch 
of electric science known as Electro Magnetism, hence this 
discovery marks one of the most important epochs in the 
progress of practical electricity. 

This exceedingly important elementary fact in electro 
magnetism can be shown in a variety of ways. 

When a wire in which the electric current is flowing is 
brought near a compass or other magnetic needle, the latter 
will be affected and tend to change its position and set itself 
at right angles to the conductor. This proves that an electric 
current flowing in a wire is in itself a form of a N. of magnet. 

Lines of Magnetic Force. — If a thin piece of paper is 
placed over a bar magnet and fine iron filings are sprinkled 
over it, the particles of iron will arrange themselves in regu- 
lar curves between the poles and to map out or define lines 
in the magnetic fields which scientists call lines of force. 
See Fig. 12. 

Fig. 10 exhibits the manner in which the filings arrange 
themselves about the ends of a horse shoe magnet. 

The forms of the curves show not only the direction of the 
magnetic force, but they also enable us to draw conclusions 
as to its intensity. When the force is great the curved lines 
are thick and sharply defined, and when it is weak the lines 
are thin aid less plain. 

The lines of force are also to be found in the neighborhood 
of wires through which electric currents are passing. They 
are the outward effect produced by the passage of an electric 
current, but the most singular fact is that they can also be the 
cause of an electric current. 



38 



NEW CATECHISM OF ELECTRICITY. 



ELECTRO MAGNETISM. 

Directions of Magnetic Force. — The direction of the mag- 
netic force in a magnetic field may be defined as the direction 
in which a small pivoted magnetic needle points when held 
in the field at that point. If a small suspended magnetic 
needle or pocket-compass be placed at various points in the 
magnetic field surrounding a bar magnet, as represented in 



.> '>^>> / 



N 



/ \ 



>. S 



/■ \ 



Fig. 13. 

Fig. 13, it will be found that the needle always points in a 
definite direction, which direction varies with its position in 
the field, the direction of the magnetic axis of the needle at 
any point representing the direction of the magnetic force at 
that point. 

If a magnetic needle, similar to that in the above experi- 
ment, be suspended by means of a thread over a bar magnet, 
and moved from the north to the south pole of the magnet, 
as illustrated in Fig. 14, the centre of the needle will trace 
out curving lines connecting the two poles. The paths or 
lines followed by the centre of the magnetic needle are 



NEW CATECHISM OF ELECTRICITY. 



39 



ELECTRO MAGNETISM. 

termed lines of magnetic force, and in the modern concep- 
tion of a magnetic field this latter is assumed to be entirely 
filled up with these imaginary lines of force. These lines of 
force are assumed, for reasons to be hereafter understood, to 
have a certain positive direction, namely that direction in 
which a small north-seeking magnetic pole would tend to 




Fig. U. 

move if placed in the magnetic field ; or, in other words, the 
lines of force are assumed to stream or flow in a direction 
from the north to the south pole, as indicated by the arrows 
in Fig. 14. 

Points Relating to Electromagnets. 

Electro-magnets are far more powerful in proportion to 
their size than steel magnets and can be made of any required 
size, those made for power stations sometimes weighing scv- ■ 
eral tons. 

Electro-magnets are used in nearly all electrical instruments 
not only because they are stronger than permanent magnets 



40 NEW CATECHISM OF ELECTRICITY. 

ELECTRO MAGNETS. 

but because they can be made to act instantly by pasing a 
current of electricity through them at the most convenient 
moment. 

The strength of an electro-magnet depends directly on the 
number of turns of wire and the current flowing through 
them. 

In an electro-magnet with an iron core, the grade of the 
iron also affects the strength — the best soft Swedish iron fur- 
nishing the strongest magnetism. 

To increase the amount of magnetism, due to a current in a 
wire at a certain point, it is only necessary to increase the 
length of wire about that point — by the operation of this law, 
the coil form of the magnet is evolved. 

The Scientific American has given an account of a great 
electro-magrj t made by Col. King several years ago at 
Willett's Point fortification, N. Y. The magnet core con- 
sisted of two old 15-inch guns, weighing 50,000 pounds each. It 
was turned into a club-footed magnet by the addition of many 
tons of heavy iron plates. The coil consisted of old torpedo 
cables 14 miles long, carrying 20 to 25 amperes. The armature 
consisted of 6 platform plates bolted together. A calculated 
force of 44,800 pounds was insufficient to tear off the armature, 
the chain used being broken by the strain. Five cannon balls, 



Note.— Inasmuch as the field-magnets of dynamos are electro-mag- 
nets, the iron cores of which are excited by electric currents circulating 
in surrounding coils, it becomes a matter of primary importance to us to 
know what is the law that governs the electro-magnet. If we once know 
the relation that subsists between the exciting current and the magnetism 
that is produced by it, we can apply this knowledge to the design of dyna- 
mos ; for such knowledge will enable us to calculate beforehand the size 
of field-magnet and the number and gauge of coils that will be required 
in a dynamo that is to furnish any given amount of electric energy. 



NEW CATECHISM OF ELECTRICITY. 4 1 

ELECTRO MAGNETS. 

of 325 pounds each, were surpended like a chain from the 
muzzle of the gun. An iron spike placed against the breast 
of a man standing three or four feet off, with his back to the 
gun, stood out straight. It required the efforts of two men 
with a sudden jerk to pull away a 25-pound bar from the 
gun. The entire mass of iron, including guns, carriages, 
armature, etc., weighed over 130,000 pounds. At a distance of 
71 feet the magnetism of the gun equaled that of the earth, a 
compass needle being deflected 45 degrees ; at a distance of 
300 feet it was deflected 3 degrees. 




42 NEW CATECHISM OF ELECTRICITY. 



ELECTRIC ENERGY, 

The production of electricity is simply a transformation of 
energy from one form into another, usually mechanical en- 
ergy is changed into electrical energy and a dynamo is sim- 
ply a device for effecting the transformation. 

Prof. Fessenden truly remarks there are two independent 
properties of matter— gravity and inertia — and these give us 
two ways of defining force and energy. 

It should always be remembered that electricity is some- 
thing real, although not easily defined. And then, too, while 
it is not matter and not energy, yet under proper conditions, 
it having the power of doing work it is convenient to speak 
of its performance as electric energy. The following ques- 
tions and answers, although few in numbei may present the 
subject with considerable clearness. 

Ques. What is energy? 

Ans. Energy is the capacity for doing work. Steam under 
pressure is an example, a spring bent ready to be released is 
another form. 

Ques. What is matter ? 

Ans. Matter is anything occupying space, which is of three 
dimensions — wide, long, deep — and which prevents other 
matter from occupying the same space at the same time. 

Ques. What is the smallest quantity of matter which can 
exist called ? 

Ans. An atom. An atom means that which cannot be cut, 



NEW CATECHISM OF ELECTRICITY. 43 

ELECTRIC ENERGY. 

scratched, or changed inform and that cannot be affected by 
heat or cold or any known force ; although inconceivably 
small, atoms possess a definite size and mass. 

Ques. What is a molecule ? 

Ans. A molecule is composed of two or more atoms. 

Ques. Why at this point are definitions most useful of 
energy and of matter ? 

Ans. Because, as stated, all electric action is an exhibi- 
tion of energy, and energy must act through matter as its 
medium. 

Ques. What is the difference between electricity and mag- 
netism ? 

Ans. The ultimate nature of neither is known. There are, 
however, some differences. To sustain a current of electricity 
requires energy. To sustain magnetism requires no energy. 



Note. — A writer in the New Science Review undertakes to answer the 
question," What is Electricity?" In order to lead the reader up to the 
main question, he first considers the natural forces, gravitation and heat. 
Examples are given of how these forces are manifested, and how energy is 
changed from one form to another. Every form of force, the author says, 
should be regarded as a different method in which energy makes itself 
known to the senses. He calls particular attention to the important fact 
that the " resistance of one kind or another is always the agent that acts 
to alter energy from one form to another," and suggests that electricity is 
simply a form or manifestation that energy may assume under given con- 
ditions, and generally is a mere transitory stage between the mechanical 
form and the heat form. " In most operations," he continues, " mechan- 
ical force passes to the heat form without passing through the electric 
form ; but whenever magnetism is brought into play as a resistance that 
must be overcome ; then mechanical power applied to overcome this re- 
sistance always becomes electricity, if only momentarily in its passage 
from the mechanical to the heat form." In conclusion, he asks if the 
question " What is Electricy ?" cannot be answered in a fairly satisfactory 
way by saying that it is simply a form that energy may assume while un- 
dergoing transformation from the mechanical or the chemical form to the 
heat form, or the reverse. 



44 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC ENERGY. 

A current of electricity is always accompanied by a magnetic 
field of peculiar form. Magnetism alone cannot produce 
electricity. Electricity can do work ; magnetism cannot do 
work in the same sense — and alike with electricity, neither 
can it exist without contact with matter. 

Ques. What is it convenient to consider, relating to these 
minute bodies ? 

Ans. That they are perpetually in motion with incredible 
velocities. 

Ques. How is energy transmitted from one part of material 
substance to another ? 

Ans. Gradually and successively. It requires a medium 
and it requires a certain time. 

Ques. What is the principal use or function in mechanics 
of electricity ? 

Ans. It is purely that of transmission. It corresponds to 
ropes, shafts and fluids as a medium of conveying and trans- 
lating power or work. 



Note.— It is evident that a body in motion has the capacity to do 
work, and a body at rest may also have the capacity to do work. In the 
first instance energy is of that kind which is due to the fact that the body 
is in motion, and has weight, and in the second, energy is due to the po- 
sition or condition of a body at rest. The ny-wheel of a steam engine in 
motion possesses kinetic energy ; a heavy weight at the top of a high 
tower possesses potential energy. 

Kinetic energy is energy due to matter being actually in motion, or 
Energy of Motion— Dynamic-energy. 

Potential or Static energy is a capacity for doing work due to advan- 
tage of position or other cause. A ten-pound weight supported one foot 
above a plane has ten foot-pounds of mechanical energy. 



NEW CATECHISM OF ELECTRICITY. 45 

EIectro=Motive Force. 

The term is employed to denote that which moves or tends 
to move electricity from one place to another. For brevity 
we sometimes write it B. M. F. In this particular case, it lit 
obviously the result of the difference of potential, and pro- 
portional to it. Just as in water pipes, a difference of level 
produces a pressure, and the pressure produces a flow so soon 
as the cap is turned on, so difference of potential produces 
electro-motive force, and electro-motive force sets up a cur- 
rent so soon as a circuit is completed for the electricity to 
flow through. Klectro-motive force, therefore, may often be 
conveniently expressed as a difference of potential, and vice 
versa ; but the reader must not forget the distinction. 

In ordinary acceptance among engineers and practical 
working electricians, electro-motive force is thought of as 
pressure, and it is measured in units called volts. The usual 
standard for testing and comparison is a special form of voltaic 
cell, called the Clark cell. This is made with great care and 
composed of pure chemicals. It is accepted as having an 
K. M. F. of i T Vo 4 o volts at a temperature of 15 degrees C. 

The term positive expresses the condition of the point hav- 
ing the higher electric energy or pressure, and, negative^ the 
lower relative condition of the other point, and the current is 
forced through the circuit by the (K. M. F.) electric pressure 
at the generator, just as a current of steam is impelled through 
pipes by the generating pressure at the steam-boiler. 



Note. — Care must be taken not to confuse electro-motive force with 
electric force or electric energy, when matter is moved by a magnet, we 
speak rightly of magnetic force ; when electricity moves matter, we may 
speak of eleetric force. But, E). M. F. is quite a different thing, not 
" force" at all, for it acts not on matter but on electricity, and tends to 
move it. 



46 



NEW CATECHISM OF ELECTRICITY. 



Fig. 15. 




Lifting Power of Magnets. 

(See page 33.) 



NEW CATECHISM OF ELECTRICITY. 



47 



PRIMARY BATTERIES. 



An electrical battery is the simplest method of generating 
electricity for practical use. Batteries all generate electricity 
by chemical action ; the great variety being caused by the 
variation of the simple elements used in all. 

The growing demand for electrical apparatus in work- 
shops, power plants, office and public buildings and dwellings 

indicates the needs of plain 
instructions whereby the en- 
gineer, electrician or other 
mechanic can arrange or man- 
age in a practical way the spe- 
cial devices ordinarily used. 

Batteries can be bought 
from supply houses all com- 
plete and ready to be set up, 
but the following pages of 
description and illustration 
will be found most useful. 

Fig. 1.6 represents a simple 
voltaic cell. 

The one fundamental fact 
Fig. 16. on which the electro-chem- 

ical generation of current depends is that, if a plate of metal 
is placed in a liquid called an electrolyte, there is a dif- 




48 NEW CATECHISM OF ELECTRICITY. 

PRIMARY BATTERIES. 

erence of electrical condition produced between them of such 
sort that the metal either takes a lower or a higher electrical 
potential than the liquid, according to the nature of the metal 
and the liquid. If two different metals are placed in one elec- 
trolytic liquid, then there is a difference of state produced 
between them, such that, if joined by a wire outside the liquid, 
a current of electricity traverses this wire. This current pro- 
ceeds in the liquid from the metal which is most acted upon 
chemically to that which is least. 

The term battery is applied to a device in which one or 
more chemical substances in a fluid mixture act upon a metal 
and a carbon, or upon two different metals, producing there- 
by a current of electricity, which will continue as long as 
there is any action of the chemicals upon the metcl a:ul car- 
bons, or upon the two metals. 

Battery connections are formed by two methods ; by the 
scries method \ as shown in Fig. 17, and the parallel method, 
Fig. 18. It will be observed that the cells are connected by 
their electrodes. 



Note. — " The popular notion of a secondary battery as a contrivance 
for storing up electricity is quite erroneous. Energy can be stored up 
but not electricity, and hence, if the term ' accumulator ' is used, it should 
be in the sense of an accumulator of energy. It is not very easy to draw a 
distinction between what should be properly called primary and what 
should be called secondary batteries. In both forms, energy is accumu- 
lated in a manner capable of being transformed into electric current, and, 
in both, this ultimately depends on chemical attraction ; but, in the forms 
of battery, usually called secondary, the chemical processes are such that 
they can be conveniently and effectively reversed by an external source of 
current, and so put bick the elements into an active condition, without 
very serious loss of available energy in so doing." — Flemming. 



NEW CATECHISM OF ELECTRICITY. 



49 



PRIMARY BATTERIES. 

The quantity of electricity generated is precisely the same 
in each method of connecting up, but the effects are quite 
different. The series gives high electric pressure and small 
volume of current, while the parallel gives low electrical 
pressure and large volume of current. 




Fig. 17. 



Ac */ gc W ^ c 





Fig. 18. 
Batteries for producing electricity are divided into two 



classes : 



1. Open circuit batteries. 

2. Closed circuit batteries. 



5° 



NEW CATECHISM OF ELECTRICITY. 



PRIMARY BATTERIES. 

An open circnit battery is one adapted by its construction 
to maintain a current that shall not run down or exhaust 
itself when left on open circuit ; for instance, where the 
electricity is not required constantly without intermission. 
This system is used in telephones, electric bells, burglar 
alarms, gas lighting, annunciators, etc. 

The closed circuit battery is used in electric motors, electric 
lighting, the electric telegraph, etc., and is adapted by its 
construction to maintain a current a long time without sensi- 
ble diminution. 

The action of the Electrical 
Battery may be briefly described 
thus : See (Fig. 19.) 
V^ ^ffl Place in a glass jar some 

water having a little sulphuric 
or other dilute acid added to it. 
Place in it separately two clean 
strips, one of zinc (Z) and one 
of copper (C). This cell is 
capable of supplying a contin- 
uous flow of electricity through 
a wire whose ends are brought 
into connection with the two 
strips. When the current flows the zinc strip is observed- to 
waste away, its consumption in fact furnishes the energy 
required to drive the current through the cell and the connect- 
ing wire. The cell may therefore be regarded as a kind of 
chemical furnace in which the fuel is the zinc. 




Fig. 19. 



NEW CATECHISM OF ELECTRICITY. 



51 



PRIMARY BATTERIES. 

If the strips are made to touch, or are joined by a pair of 
metal wires, immediately there is a rush of electricity, through 
the metal from the copper to the zinc, and a small portion of 
the zinc is at the same time dissolved away ; the zinc parting 
with its latent energy as its 
atoms combine with the acid. 
This energy is expended in 
forcing a discharge of electric- 
ity through the acid to the 
copper strip, and thence 
through the wire circuit back 
to the zinc strip. 




Fig. 20. 



The real starting point is in 
the cell at the surface of the 
zinc where the chemical action 
is furnishing energy ; for from 
this point there are propagated 
through the liquid certain 
electro-chemical actions which 
have the result of constantly 
renewing the difference of po- 
tential and supplying electricity to the -f- pole just as fast 
as that electricity leaks away. 

ELECTRIC BATTERIES. 

Smee's Battery is shown in Fig. 21 ; it is frequently termed 
the Smee Cell. It was devised in the year 1830 by Alfred 
Smee, an English electrician, and has been very extensively 
used, and consists of a platinized silver plate for the negative 



NEW CATECHISM OF ELECTRICITY. 



:l- 



JL 



:!=. 



1 



ELECTRIC BATTERIES. 

element, with zinc plates for the positive. The platinized 
silver plate is usually attached to a wooden bar, and the zinc 
plates, placed one on each side of it, are kept in position by a 
metallic cramp passing over the top of the bar. A binding 

screw, passed through the wooden 
bar and attached to the silver 
plate, forms the anode, and a sim- 
ilar binding screw, on the cramp 
that holds the zincs to the bar, is 
the cathode. An earthenware con- 
taining- vessel is required ; the bat- 
tery is excited by dilute sulphuric 
acid (7 volumes of water to one of 
acid). This battery is admirably 
adapted for electro-depositing and general galvanic experi- 
ments ; but it is not suitable for producing electric light, nor 



Fig. 21. 



for intensity coils. It is easily 
managed, tolerably constant, and 
requires only one exciting fluid ; 
therefore, porous cells are dis- 
pensed with. 

The Bun sen Cell, or Battery, 
shown in Fig. 22 is a two-fluid cell 
constructed with zinc and carbon 
electrodes. The negative plate is 
carbon, the positive plate amal- 
gamated zinc. The excitant is a dilute solution of sulphuric 
acid. The top part of the carbon is sometimes impregnated 




Fig. 22. 



NEW CATECHISM OF ELECTRICITY. 



53 



ELECTRIC BATTERIES. 

with paraffin wax to keep the acid from creeping up, and 
electrotyped with copper. 

The force of the Bunsen increases after setting up for about 
an hour, and the full effect is not attained until the acid soaks 
through the porous cell. Carbons are not effected, and last 
any length of time. The zinc is slowly 
consumed, through the mercury coating. 

" With one exception, Bunsen's is the 
only real producer of voltaic currents that 
can be cheaply applied and depended 
upon in the production of electric light. 
Its current, once started, is almost con- 
stant for about four hours, and a good 
light may, with confidence, be depended 
upon for three hours."— Urquhart. 



A I 

i r-" El 


Xc?fi — ~ 



Fig. 23. 




The Leclanche Battery or cell was invented by Leclanche, 
a French electrician, and was the first battery cell in which 
sal-ammoniac was used. This form of ^p 
battery, Fig. 23, is in very general use 
for electric bells, its great recommen- 
dation being that, once charged, it 
retains its power without attention 
for several years. Two jars are em 
ployed in its construction ; the outer 
cne is of glass, contains a zinc rod, 
and is charged with a solution of am- 
monium chloride (sal ammoniac). Fig. 24. 
The inner jar is of porous earthenware, contains a carbon 




NEW CATECHISM OF ELECTRICITY. 



ELECTRIC BATTERIES. 

plate, and is filled up with a mixture of manganese peroxide 
and broken gas carbon. When the carbon plate and the 
zinc rod are connected, a steady current of electricity is 
set up, the chemical reaction which takes place being as fol- 
lows : The zinc becomes oxidized by the oxygen from the 
manganese peroxide, and is subsequently converted into zinc 
chloride by the action of the sal-ammoniac. After the bat- 
tery has been iii continuous use for some hours, the manga- 
nese becomes exhausted ot oxygen, and the force of the 
electrical current is greatly diminished ; but if the battery be 
allowed to rest for a short time, the manganese obtains a 
fresh supply of oxygen from the atmosphere, and is again fit 
for use. After about 18 months* work, the glass cell will 
probably require recharging with sal-ammoniac, and the zinc 
rod may also need renewing ; but should the porous cell get 
out of order, it is better to get a new one entirely than to 
attempt to recharge it. — Dye^r. 

Gravity Cells or batteries (see figure 24). Instead of 
employing a porous cell to keep the two liquids separate, 
it is possible, where one of the liquids is heavier than the 
other, to arrange that the heavier liquid shall form a stratum 
at the bottom of the cell, the lighter floating upon it. 

Such arrangements are called gravity cells > but the separa- 
tion is never perfect, the heavier liquid gradually diffusing 
upwards. 

In Fig. 24 is shown the method which has been adopted of 
placing the zinc in the upper part of the cell and the copper 
in the lower part. The solution of the zinc sulphate which 



NEW CATECHISM OF ELECTRICITY. 



55 



ELECTRIC BATTERIES. 

surrounds the zinc is lighter than the copper sulphate which 
surrounds the copper. Fig. 25 represents the " Crowfoot " 
Gravity Battery, largely used for Telegraph and closed curcuit 
work. 

After the cell is set up sufficient time must be allowed to 
form these two sulphates before free action is attained. 

The Daniell Battery consists of a copper cylinder contain- 
ing another of porous earthenware, in which is placed a zinc 
rod ; this latter forms the positive and 
the copper the negative element. The 
battery requires 2 excitants — a saturated 
solution of copper sulphate in the cop- 
per cylinder, and dilute sulphuric acid 
(1 volume oil of vitriol to 7 of water) in 
the porous cell. The walls of the latter 
keep the solutions separate, while allow 
ing the electric current to pass through. 

The cathode and anode are formed 
by attaching binding screws to the zinc 
rod and copper cylinder. The battery requires no frame, is 
effective in use, constant, and gives a current of fair intensity. 
Latimer Clark's Standard Cell. — A standard cell whose E. 
M. F. is even more constant than that of the Daniell was 
suggested by Latimer Clark. This battery is composed of 
pure mercury, on which floats a paste of mercurous sulphate, 
a plate of zinc resting on the paste. Contact with the mercury, 
which acts as the positive pole, is made with a platinum wire. 
The E. M. F. is 1.436 legal volts. 




Fig. 25. 



56 NEW CATECHISM OF ELECTRICITY. 



DEFINITIONS RELATING TO PRIMARY BATTERIES. 

The Voltaic-cell is very commonly called the voltaic battery 
after its discoverer, Volta, and more recently named the 
primary battery, to distinguish it from the secondary or stor- 
age battery. 

A cell consists of a vessel containing a liquid in which two 
elements are immersed. In One Fluid cells both electrodes 
are immersed in the same solution. In Two Fluid cells each 
electrode is immersed in a separate solution, one of which is 
contained in a porous cup which is then immersed in the other 
liquid. 

Dry cells are similar in construction to the open circuit, 
one fluid cell. The only difference being that starch or some 
other absorbent is mixed with the liquid forming a jelly which 
is not easily spilled. The dry cell is very efficient, but when 
once exhausted is of no further use. 

All dry cells should have vent holes. 

The Electrodes of a Primary Battery are the plates of metal 
or other substance immersed in the liquid. The zinc plate is 
called the generating electrode and the other plate the con- 
ducting electro. The latter is usually made of carbon, copper 
being the next most commonly used. 



Note. — The plates in a galvanic couple are termed elements as the 
carbon and zinc plates in cell. The plate unattacked by the solution as 
the carbon plate in the above battery is termed the negative plate or 
element ; the one attacked, as the zinc plate, is termed the positive plate or 
element. 



NEW CATECHISM OF ELECTRICITY. 57 

DEFINITIONS-PRIMARY BATTERIES. 

The Poles of a battery are the parts of the Electrodes which 
project out of the liquid. They are distinguished from each 
other by -f- f° r the positive and — for the negative pole. The 
terms Pole or Terminal apply to the ends of a break in any 
electric circuit. 

The Exciling Fluid is the liquid which when plates are 
placed in it acts upon the plates and produces a current in a 
wire joining the two plates. 

The eleclrolyte is another term for the exciting fluid. 

The Anode is the plate which the current leaves to enter 
the liquid of the cell as it flows through the circuit of that 
battery. 

The Kathode (or Cathode) is the plate the current enters as 
it leaves the liquid of the cell as it flows through the circuit 
of that battery. 

Polarization is the weakening of the battery current" by 
means of local action ; this is commonly caused by the collec- 
tion of hydrogen bubbles on the copper plate. Polarization is 
overcome in two ways, namely, chemically and mechanically. 
In the first mentioned a solution or substance which will 
absorb the free hydrogen is introduced in the cell. In the 
second the plates have a roughened surface and are kept 
moving in the solution. 

Local Action. — When the circuit is not closed the current 
cannot flow, and there should be no chemical action so long 
as the battery is producing no current. The impure zinc of 
commerce, however, does not remain quiescent in the acid, 



58 NEW CATECHISM OF ELECTRICITY. 

DEFINITIONS-PRIMARY BATTERIES. 

but is continually dissolving and giving off hydrogen bubbles, 
causing local action. The impurities in the zinc consists of 
particles of iron, arsenic, and other metals. 

Separating the elements. — Obviously the positive and nega- 
tive elements of a battery must not be in contact within the 
exciting fluid ; they should be separated by a space of y% to %, 
inch. In the case of batteries without porous cells, periodical 
attention will need to be given to ensure this condition being 
maintained. 

Electrolysis is the decomposition of a chemical compound 
by the electric current. 

Bichromate Batteries of bottle shape as in Fig. 20, with 
two carbon plates, a sliding rod and movable zinc plate, are 
very extensively used by experimenters and lecturers, because 
they are always ready for being put to work with one motion 
of the hand, not necessitating any other preparation ; and as 
soon as the desired result is obtained, the battery can be put 
out of action with the same facility. 



NEW CATECHISM OF ELECTRICITY. 



59 



MANAGEMENT AND CARE OF BATTERIES. 



Cleanliness in the battery-room is essential to the best 
results. The jars, before being used, should be coated with 
parafine wax for an inch or so from the top. This prevents 
1 ' creeping" of the salts and consequent weakening cf the 
battery fluid. Zincs and coppers, or their homologous ele- 
ments, should be thoroughly cleaned every time the cell is 
taken out of use. The zinc, after being thoroughly cleaned, 
should be rubbed with a little mercury. This prevents local 
action. Porous cups should be soaked in clean water four or 
five hours and then wiped dry. If the cells are cleaned and 
put away ready for use, when the emergency does come, the 
time spent in cleaning will never be regretted. 

Fig. 26. 




The Crown of Caps. 



6o NEW CATECHISM OF ELECTRICITY. 



THE MAGNETIC AND ELECTRIC CURRENT. 



This branch of science comes naturally under the head of 
Current Electricity, but, 

To give a definition of the electric current is like attempt- 
ing Jo describe something which every one knows about ; it 
can be said to be simply the flow of electric energy from a 
point of high pressure to that of a lower, yet it must be owned 
that until we know with absolute certainty what electricity is 
we cannot expect to know precisely what a current of elec- 
tricity is. 



Note — The circuit may be compared to a system of hot- water pipes ; in 
a hot-water system there is a steam boiler, a flow and a return circulating 
pipe with pipe coils, at various points for giving off heat where warmth 
is required. 

In an electric installation the dyamo or battery replaces the boiler ; 
flow and return pipes are represented by the two conducting mains and 
the pipe-coils by lamps, motors and other apparatus. 

In a hot- water system it is perfectly evident that whatever may be the 
quantityof water leaving the boiler, the same must return to it and the 
quantity of water passing through every part of the flow and return pipes 
in a given time' must be alike. 

It is so with the electric current ; whatever may be the quantity of the 
current starting from the dynamo the same quantity comes back to it. 

Also, the whole of this quantity must pass through the mains, but it is 
different with the pressure ; this diminishes in proportion to the work 
done by the current. Consequently the pressure diminishes as the cur- 
rent advances along its path. 

Comparing this again with the hot-water system, the analogy is fairly 
complete ; for the current may be regarding as losing heat (this is often 
disguised) as it advances, since in losing its pressure it produces heat and 
the hot water does the same. 



NEW CATECHISM OF ELECTRICITY. 6l 

MAGNETIC AND ELECTRIC CURRENT. 

Ques. — In cases where part of the electricity is transferred 
from the body originally electrified to the body touched what 
is this transfer, of electricity called? 

Ans. — It is called a discharge. 

Ques. — When does a discharge of electricity become a 
current ? 

Ans. — When electricity is supplied to the body as fast as 
it is taken away. 

In considering the practical questions relating to the electric 
current three characteristic effects need to be thought of : 

i. The chemical. 

2. The thermal (heat). 

3. The magnetic. 
All lines of magnectic force from closed circuits and an 
electric circuit, so called, may be said to be the path in which 
electricity passes from a given point around a conducting 
point back again to its starting point. 

The discovery of electric currents originated with Galvani, 
a physician of Bologna, who about the year 1786, made a series 
of curious and important observations upon the convulsive 
motions produced by the " return shock " and other electric 
discharges upon a frog's leg. 

This immortal discovery arose in the most immediate and 
direct manner, from an indisposition with which a Bolognese 
lady was affected, for which her medical adviser prescribed 
frog -broth. 

Galvani, the husband of the lady, was Professor of Anatomy 
in the University of Bologna. It happened that several frogs, 



62 NEW CATECHISM OF ELECTRICITY. 

MAGNETIC AND ELECTRIC CURRENT. 

prepared for cooking, lay upon the table of his laboratory, 
near to which his assistant was occupied with an electrical 
machine. On taking sparks from time to time from the con- 
ductor, the limbs of the frogs were afFeeted with convulsive 
movements resembling vital actions. 

This was the effect of the inductive action of the electricity 
of the conductor upon the highly electroscopic organs of the 
frogs ; but Galvani was not sufficiently conversant with this 
branch of physics to comprehend it, and consequently regarded 
it as a new phenomenon. He proceeded to submit the limbs 
of frogs to a course of experiments, with the view to ascertain 
the cause of what appeared to him so strange. For this 
purpose, he dissected several frogs, separating the legs, thighs, 
and lower part of the spinal column from the remainder, so as 
to lay bare the lumbar nerves. He then passed copper hooks 
through that part of the dorsal column which remained above 
the junction of the thighs, without any scientific object, but 
merely for the convenience of suspending them until required 
for experiment. It chanced, also, that he suspended these copper 
hooks upon the iron bar of the balcony of his window, when, 
to his inexpressible astonishment, he found that whenever the 
wind or any other accidental cause brought the muscles of the 
leg into contact with the iron bar, that a similar convulsive kick 
was produced in the frog's leg. 

Galvani imagined this action to be due to electricity 
generated by the frog's leg itself. It was, however, proved by 
Volta, Professor in the University of Pavia, that the electricity 
arose not from the muscle or nerve, but from the contact of 



NEW CATECHISM OF ELECTRICITY. 63 



MAGNETIC AND ELECTRIC CURRENT. 

the dissimilar metals. A greater accumulation of electric 
energy at one point than at another is what causes the electric 
current. Such a current always flows through a conducting 
body if the ends are kept at a different electrical pressure. 

In order that a continuous flow may be kept up there must 
be a circuit provided. Currents are called continuous if they 
flow without stopping in one direction. They are called 
alternate currents if they continually reverse in direction in a 
regular periodic manner, flowing first in one direction round 
the circuit and then in the other. 

The flow would cease unless the difference in electric pressure 
is maintained ; this can be done by either a battery or dyna- 
mo. The current is impelled through the circuit by the elec- 
tric pressure at the battery or dynamo just as a current of 
steam is impelled through pipes, of whatever form, by the 
pressure of the steam formed in the boiler. 

All dynamos, of whatever form, are based upon the discovery 
made by Faraday in 183 1, that electric currents are generated in 
conductors by moving them in a magnetic field. Faraday's prin- 
ciple may be enunciated as follows : " When a conductor is 
moved in a field of magnetic force in any way so as to cut the 
lines of force, there is an electromotive-force produced in the 
. conductor, in a direction at right angles to the direction of 
the motion, and at right angles also to the direction of the 
lines of force, and to the right of the lines of force, as viewed 
from the point from which the motion originates." 

To understand clearly Faraday's principle — that is to say, 
how is it that the act of moving a wire so as to cut magnetic 



6 4 



NEW CATECHISM OF ELECTRICITY. 



MAGNETIC AND ELECTRIC CURRENT. 

lines of force can generate a current of electricity in that wire 
— let us repeat and further explain this. 

A wire through which a current of electricity is flowing 
looks in no way different from any other wire. No man has 
ever yet seen the electricity running along in a wire, or knows 




-'wmm 



Fig. 27. 



precisely what is happening there, but no electrician is in any 
doubt as to one most vital matter, namely, that when that 
which is called an electric current flows through a wire, the 
magnetic forces with which that wire is thereby, for the time, 
endowed, resides not in the wire at all, but in the space sur- 
rounding it. Kvery one knows that the space or "field" 
surrounding a magnet is full of magnetic "lines of force, " 



NEW CATECHISM OF ELECTRICITY. 65 

MAGNETIC AND ELECTRIC CURRENT. 

and that these lines run in tufts from the N -pointing pole to 
the S-pointing pole of the magnet, invisible until, by dusting 
iron filings into the field, their presence is made known, 
though they are always in reality there (Fig. 27). A view of 
the magnetic field at the pole of a bar magnet, as seen end-on, 
would, of course, exhibit merely radial lines, as seen in Fig. 
28. 




Fig. 28. 

Now, every electric current (so-called) is surrounded by a 
magnetic field, the lines of which can be similarly revealed. 
To observe them, a hole is bored through a card or a piece of 
glass, and the wire which carries the current must be passed 
up through the hole. When iron filings are dusted into the 
field they assume the form of concentric circles (Fig. 12), 



66 



NEW CATECHISM OF ELECTRICITY. 



Fig. 29. 




MAGNETIC AND ELECTRIC CURRENT. 

showing that the lines of force run completely round the wire, 
and do not stand out in tufts. In fact, every conducting wire 
is surrounded by a sort of magnetic whirl, like that shown in 
Fig. 29. A great part of the energy of the so-called electric 
current in the wire consists in these external 
magnetic whirls. To set them up requires 
an expenditure of energy ; and to maintain 
them requires also a constant expenditure of 
energy. It is these magnetic whirls which 
act on magnets and cause them to set as gal- 
vanometer needles do at right angles to thej 
conducting wire. 

Now, Faraday's principle is nothing 
more nor less than this : that by moving a, 
wire near a magnet across a space in which, 
there are magnet lines, the motion of the: 
wire, as it cuts across those magnetic lines,, 
sets up magnetic whirls round the moving 
wire, or, in other language, generates a so- 
called current of electricity in that wire. 

It is however necessary that the moving 
conductor should, in- its motion, so cut the 
magnetic lines as to alter the number of lines 
of force that pass through the circuit of which 
the moving conductor forms part. If a con- 
ducting circuit — a wire ring or single coil, for 
example — be moved along in a uniform mag- 
netic field, so that only the same lines of force pass through it, 
no current will be generated, see Fig. 30. Or if, again, as in 



MAGNETIC WHIRL 

SURROUNDING 
WIRE CARRYING 

CURRENT. 



NEW CATECHISM OF ELECTRICITY. 67 

MAGNETIC AND ELECTRIC CURRENT. 

Fig. 31, the coil be moved by a motion of translation to 
another part of the uniform field, as many lines of force 
will be left behind as are gained in advancing from its first 
to its second position, and there will be no current gener- 
ated in the coil. If the coil be merely rotated on itself 
round a central axis, like the rim of a fly-wheel, it will not 
cut any more lines of force than before, and this motion will 
generate no current. But if, as in Fig. 32, the coil be tilted 
in its motion across the uniform field, or rotated round any 
axis in its own plane, then the number of lines of force that 
traverse it will be altered, and currents will be generated. 
These currents will flow round the ring coil in the right- 
handed direction (as viewed by a person looking along the 
magnetic field in the direction in which the magnetic lines 
run ) if the effect of the movement is to diminish the number 
of lines of force that cross the coil ; they will flow round in 
the opposite sense, if the effect of the movement is to increase 
the number of intercepted lines of force. 

If the field of force be not a uniform one, then the effect 
of taking the coil by a simple motion of translation from a 
place where the lines of force are dense to a place where they 
are less dense, as from position 1 to position 2 in Fig. 32, 
will be to generate currents. Or, if the motion be to a place 
where the lines of force run in the reverse direction, the 
effect will be the same, but even more powerful. 



08 



NEW CATECHISM OF ELECTRICITY. 



MAGNETIC AND ELECTRIC CURRENT. 



Fig. 30. 




CIRCUIT MOVED WITHOUT CUTTING ANY LINES OF FORCE. 



Fig. 31. 




CIRCUIT MOVED SO AS TO ALTER NUMBER OF LINES OF 
FORCE THROUGH IT. 



NEW CATECHISM OF ELECTRICITY. 



69 



MAGNETIC AND ELECTRIC CURRENT. 

We may now summarize the points under consideration 
and some of their immediate consequences, in the following 
manner : 

(1.) A part, at least, of the energy of an electric current 
exists in the form of magnetic whirls in the space surround- 
ing the conductor. 

Fig. 32. 




(2.) Currents can be generated in conductors by setting up 
magnetic whirls round them. 

(3.) We can set up magnetic whirls in conductors by mov- 
ing magnets near them, or moving them near magnets. 



Note. — As a matter of fact, it would be impossible to have a magnetic 
field exactly like Fig. 32 ; for, in the intermediate part, between the upper 
and lower fields, the magnetic lines would be of curved complex form. 



70 NEW CATECHISM OF ELECTRICITY. 



MAGNETIC AND ELECTRIC CURRENT. 

(4.) To set up such magnetic whirls, and to maintain them 
by means of an electric current circulating in a coil, requires 
a continuous expenditure of energy, or, in other words, con- 
sumes power. 

(5. ) To induce current in a conductor, there must be rela- 
tive motion between conductor and magnet, of such a kind as 
to alter the number of lines or force embraced in the circuit. 

(6.) Increase in the number of lines of force embraced by 
the circuit produces a current in the opposite sense to de- 
crease. 

(7.) Approach induces an electromotive-force in the op- 
posite direction to that induced by recession. 

(8.) The more powerful the magnet-pole or magnetic field 
the higher will be the electromotive-force generated. 

(9.) The more rapid the motion, the higher will be the 
electromotive-force. 

(10.) By joining in series a number of such moving con- 
ductors, the electromotive-forces in the separate parts are 
added together ; hence very high electromotive- forces can be 
obtained by using numerous coils properly connected. 

(11.) Since the quantity or strength of the currents depends 
on the resistance of the conductors in the circuit, as well as 
on the electromotive-force, all unnecessary resistance should 
be avoided. 

(12.) Approach being a finite process, the method of 
approach and recession (of a coil towards and from a mag- 



NEW CATECHISM OF ELECTRICITY. 7 1 

MAGNETIC AND ELECTRIC CURRENT. 

net pole) must necessarily yield currents alternating in 
direction. 

(13.) By using a suitable commutator, all the currents, 
direct or inverse, produced during recession or approach, can be 
turned into the same direction in the wire that goes to supply 
currents to the external circuits ; and if the rotating coils are 
properly grouped so that before the electromotive-force in one 
set has died down another set is coming into action, then it 
will be possible, by using an , appropriate commutator, to 
combine their separate currents into one practically uniform 
current. 

(14.) To the moving conductor which is generating the 
electromotive-force by cutting the magnetic lines, it makes 
no difference what the origin of those lines is, whether from 
a permanent magnet of steel or from an electro-magnet, pro- 
vided the number of magnet lines so cut is the same. 

(15.) To the moving conductor it makes no difference what 
'the origin of the motion is. Whether the motion be due to a 
steam engine, or to a gas engine, or to hand driving, or to 
the driving of an electric current in the wire itself (as in the 
case of electric motors), it makes no difference to the moving 
conductor, which provided that the speed and the number of 
magnet lines given will generate the same electromotive- 
force. 



72 NEW CATECHISM OF ELECTRICITY. 



ANIMAL ELECTRICITY. 



Animal Electricity, — Several species of cretures inhabiting 
the water have the power of producing electric discharges by 
certain portions of their organism. The best known of these 
are the Torpedo, the Gytnnotus, and the Silurus, found in the 
Nile and the Niger. The Klectric Ray, of which there are 




THE ELECTRIC E£L> 

three species inhabiting the Mediterranean and Atlantic, is 
provided with an electric organ on the back of its head, as 
shown in illustration on this page. This organ consists of 
laminae composed of polygonal cells to the number of 800 or 
1000, or more, supplied with four large bundles of nerve fibres ; 
the under surface of the fish is — , the upper -(-. In the Suri- 
nam eel, the electric organ goes the whole length of the body 
along both sides. It is able to give a most terrible shock, and 
is a formidable antagonist when it has attained its full length 
of 5 or 6 feet. 



NEW CATECHISM OF ELECTRICITY. 73 



POINTS " RELATING TO THE ELECTRIC 
CURRENT. 



To designate the character of a current, and also a current 
with reference to its origin, various terms are used. Battery 
current, dynamo current, earth current, etc. These are terms 
used to designate the current from a battery, a dynamo or 
currents flowing through the earth on account of difference 
of potential at different points. 

When a difference of electrical force or pressure exists in 
two places connected by a conductor, or a series of conducting 
bodies, a current will flow between the two points. The dif- 
ference of force may be due to several causes, but whatever 
the cause the current will flow. The two places may be a few 
inches apart, as in a wire from a primary battery, or miles 
apart, as in a transmission system, or in the currents of the 
earth or air. They may be connected by a small copper wire, 
the rails of a street railway, or by a combination of a large 
number of conducting bodies. This conductor may be of 
large capacity, of low resistance, or may be a poor conducting 
medium. 

Two kinds of current are generated, distinguished by the di- 
rection which they flow. The continuous or direct current 



74 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC CURRENT. 

which flows continuously in one direction, and the alternating 
reversed current, which alternates the direction of its flow are 
the currents used, and these two kinds include a number of 
classes. 

The alternating current may alternate the direction in 
which it flows ten thousand times a second, or twenty -five 
times a second ; this is called the frequency of its alterna- 
tions. 

A constant current is an unvarying current. Although the 
voltage may vary the amount of current does not change. In 
series arc lighting systems the current is universally constant. 

The quantity of electricity conveyed by a current is propor- 
tional to the current and the time it continues to flow. 



Note. — The telegraphers have made a series of tests for the purpose of 
ascertaining the actual amount of time which elapses while a signal is be- 
ing flashed from America to Europe along the Atlantic cable. The tests 
referred to were made at the McGill University, Montreal, Canada, in 
June, 1891. In carrying out these experiments a duplex circuit was 
arranged dii both land and sea along the entire line, which connects Mon- 
treal with Waterville, Ireland. When the line was '* cleared " a chrono- 
graph was attached to the observatory wire at Montreal and everything 
declared in readiness. The instrument clicked off the signal, while the 
experimenters watched the chronograph with breathless interest. It 
did not seem to them " like an age of suspense," however, for within one 
and one-eighth seconds the chronograph recorded the return of the sig- 
nal, while it slowly dawned upon the interested scientists present that the 
flash had actually made the round trip from Montreal to Ireland in a pe- 
riod of time but little greater than one-sixtieth of a minute. In that very 
short space of time, infinitesimal and almost unthinkable that electric 
message was flashed a distance almost as great as one-third the circum- 
ference of the world, or to be exact, 8,022 miles. Other experiments made 
the same day showed a variation of from one to i.r seconds for the signal 
to make a round trip. 



NEW CATECHISM OF ELECTRICITY. 75 

ELECTRIC CURRENT. 

The passage of a current through a conductor cannot be ef- 
fected without a loss of power i. e. , diminished pressure. 

Loss of power means work done ; if this work has a useful 
purpose it is not a loss in the common sense of the word, but 
in all other cases it is waste. Thus, any pressure of the cur- 
rent used in a lamp is no loss and nearly the whole pressure 
of the current, in a well designed installation, may be regarded 
as utilized in passing through the lamps, motors and other 
apparatus, a system shown. 

The electric current, like steam and water flows in the di- 
rection of the least resistance. This is a general statement, to 
be modified by the fact that where two or more paths exist 
some current will pass through each. See page 79, "Divided 
Currents." 

The speed of the electric current has been quite accurately 
determined to be identical with that of light. 

Experiments have demonstrated the remarkable fact that 
alternating currents of a tension ten times that which is used 
in electro execution do not effector injure the human body 
when passed through the same ; and in fact are hardly per- 
ceptible in case the currents alternate 100,000 times in a 
second, that is, change their direction at this almost incom- 
prehensible velocity. 



7 6 



NEW CATECHISM OF ELECTRICITY. 



THE SOLENOID. 
Fig. 33. 




BAR MAGNET SHOWING WNES OF FORCE). 



Fig. 34. 




n 



r\ 



a 



u 



n 



w 



jQl 



p" 



JQ 



o 



uhreclurrv of 
Uli££ offorcoi. 



# 



ELECTRO MAGNET SHOWING LINKS OF FORCE. 



Fig. 35. 




Current, 
leaves 



CurrercU 
enUrs 



SOL.ENOID SHOWING LINES OF FORCE. 



NEW CATECHISM OF ELECTRICITY. 7 7 

THE SOLENOID. 

Solenoids. — If a wire, while being traversed by an electric 
current, is wound up into a spiral coil, the arrangement 
becomes a "solenoid." (See Fig. 35.) 

For with a long closely wound spiral, conveying a current, 
the lines of force are similar to those of a bar-magnet. (See 
Fig- 33-) These lines of force must be thought of as closed 
loops linked with the current. The conductor conveying the 
current passes through all the loops of force, and these are, so 
to speak, threaded or slung on the current line of flow. It 
will be readily inferred that since a solenoid of wire convey- 
ing a current attracts and repels by its extremities the poles 
of a magnet, two such spiral conductors conveying currents 
should attract and repel each other. This is found to be the 
case. 

The lines of force form continuous closed curves running 
through the interior of the coil, and issuing from one end and 
entering into the other end of the coil, and that the arrange- 
ment of the external magnetic field is very similar to that of 
a permanent bar magnet of cylindrical form as represented in 
Big. 34. 

A solenoid has north and south poles, and in fact possesses 
all the properties of an ordinary permanent magnet, with the 
important difference that the magnetism is entirely under 
control, for it is found that under all circumstances the 
strength of the magnetic field of a solenoid is at every point 
proportional to the strength of the electric current passing 
through its coils ; if the current is increased, the magnetism 
is increased in proportion also ; and if the current is stopped, 



78 NEW CATECHISM OF ELECTRICITY. 

THE SOLENOID. 

all trace of magnetism disappears. The magnetic effect or 
the magnetising power of a solenoid is also proportional to the 
number of turns of wire composing the coil. 

As previously mentioned, the strength of the magnetic field 
of a solenoid is strictly proportional to the strength of the 
current flowing in its coils ; this, however, is no longer true 
when the solenoid is provided with an iron core or becomes 
an electro magnet, for the reason that the magnetic properties 
of the iron alters with the strength of the magnetic field. 

At first, the presence of the iron enormously increases the 
strength of the field ; after a time, however, as the strength 
of the current flowing in the exciting coils is increased, the 
conductibility of the iron for the lines of force appears to 
decrease, until a point is eventually reached when the pres- 
ence of the iron core appears to have no effect whatever in 
increasing the strength of the field. 

At this stage the iron core may be regarded as being 
saturated with lines of force, and any further increase of mag- 
netising power will produce only a slight increase in the 
strength of the field, any such increase being that due to the 
effect of the coils alone acting merely as a simple solenoid. 

Current Sheets — When a current enters a solid conductor 
it no longer flows in one line but spreads out and flows 
through the mass of the conductor. When a current is led 
into a thin plate of conducting matter it spreads out into a 
' ' current sheet ' ' and flows through the plate in directions 
that depend upon the form of the plate and the position of 
the pole by which it returns to the battery. 



NEW CATECHISM OF ELECTRICITY. 79 

CURRENT SHEETS. 

Thus, if wires from the two poles of battery are brought 
into contact with two neighboring points in the middle of a 
very large flat sheet of tinfoil, the current flows through the 
foil not in one straight line, but in curving " lines of flow," 
which start out in all directions and curl round to meet in 
curves very like those of the " lines of force." that run from 
the N pole to the S pole of a magnet (Fig. 14). When the 
earth is used as a return wire to conduct the telegraph currents, 
a similar spreading of the currents into current "sheets occurs. 

Divided Circuits. — If a circuit divides into two branches, 
uniting together again, the current will also be divided, part 
flowing through one branch part* through the other. The 
relative strengths of current in the two branches will be pro- 
portional to their conductivities, i. e., inversely proportional 
to their resistances. 

Direction of Lines of Electrical Force. — The direction of 
the lines of force is found at any spot by holding a small mag- 
netic test-needle at that point and noting the direction in 
which it sets, and the direction of its marked or north pole. 

Various rules have been given for recollecting the direction 
of the current induced in a conductor when moved so as to 
cut lines of magnetic force and alter the amount of magnetic 
induction passing through the circuit. These rules depend 
generally on some association with the position and motion in 
swimming, or upon the direction of the cardinal points and 
the motion of the sun, earth, etc. Apart from the difficulty 
of recollecting the rules themselves, it requires an effort of 



NEW CATECHISM OF ELECTRICITY. 



DIRECTION OF ELECTRIC CURRENT. 

imagination to apply them to the case of an armature, bar or 
wire, disc or loop, and as a means of economising time and 
brain labor the following rule by Prof. Flemming has been 
found very useful. 

" If any circuit is being moved in a magnetic field, and it is 
required to know the direction in which electricity is being 
urged in any portion of the circuit which is cutting lines of 
force, proceed as follows : Hold the first and middle fingers 
and thumb of the right hand in a position as nearly as possible 
at right angles to each other, so as to represent three axes in 
space. Make the following associations. Let the direction 
of the forefinger represent the direction of the ♦lines of force. 
Let the direction of the thumb represent the direction at right 
angles to the direction of the field in wich the element of the 
circuit is moving, then the direction of the middle finger 
represents the direction of the induced current. ' ' See Fig. 36. 

In railroad work now becoming of primary importance, 
i t is always understood that the current flows out on the trolley 
wire and comes back through the rail or by the return conduc- 
tor connected to the rail. This return conductor being some- 
times placed underground and some instances upon poles with 
underground connection to the rail every six or eight poles. 



Note. — The following rule gives the relation of the electric current 
to the lines of magnetic force produced by it. 

If you look at the positive (or north) end of an electro-magnet, the 
direction of the current setting up the magnetism is that of positive rota- 
tion. Similar^, it you imagine a s ction made in a conductor carrying a 
current and look at the positive end of this conductor ( i. e., the end from 
which the current is flowing) the direction of lines of force set up about 



NEW CATECHISM OF ELECTRICITY. 



FLEMING'S RULE. 

Fig. 36. 



Direction of 
< 




Right 


Hand, 


Y 


eA 








Motion. 


**$£ 





> X 



Illustration of Fleming's Rule. 

Fleming's Rule : " Hold the thumb and the first and the middle 
fingers of the right hand as nearly as possible at right angles to each 
other, as in Fig. 36, so as to represent three rectangular axes in space. If 
the thumb points in the direction of the motion, and the forefinger points 
along the direction of the magnetic lines, then the middle finger will 
point in the direction of the induced electro-motive force." 



82 



NEW CATECHISM OF ELECTRICITY. 



DIRECTION OF ELECTRIC CURRENT. 

the conductor in the direction of positive rotation. Conversely, if you 
look at the negative (south) end of a solenoid, the direction of the current 
is that of negative rotation, and if you look at the negative end of a 
conductor (*'. <?., imagine a section without really breaking the circuit) the 
direction of the lines of force about it will be that of negative rotation. 

Kvery student of electrical engineering knows that positive rotation, 
mathematically speaking, is opposite to the hands of a watch, and he also 
knows what is meant by the positive end of a magnet and the positive 
terminal of a conductor. Accordingly, if he remembers the rule at all, he 
cannot make a mistake, like substituting " right hand " for " left hand," 
or " clockwise " for " anti-clockwise." It is a positive rule ; positive and 
means positive rotation and positive rotation gives positive end. — B. S. 

IyAMPHER. 



Fig. 37. 




NEW CATECHISM OF ELECTRICITY. 83 



ELECTRO-MAGNETIC INDUCTION. 



One of the great discoveries made by Faraday was that of 
induction or induced currents. While experimenting with 
electricity and magnetism he found that if he took a wire, 
joined the ends and moved it rapidly in front of a magnet, a 
current would be induced in the wire. This action of the 
magnet is called electro -magnetic induction. The current is 
called the induction or induced current and it is upon this 
principle discovered by Faraday that all dynamo electric 
machinery is based, as well as induction coils, alternate current 
transformers and other electrical appliances. 

When it was discovered that an electrical spark — which is 
a transient electric current — would not pass through a vacuum, 
that it would jump three feet in the air rather than bridge the 
eighth of an inch where there was no conducting material ; 
it became apparent that empty space was a perfect non-con- 
ductor of electricity ; nevertheless, by this process called 
induction, one body may become electrified by the mere 
presence of another electrified body without contact with 
it, just as a body may be heated by another body without 
contact. 

When a wire, charged with a heavy current of electricity 
is strung parallel for a considerable distance to another wire, 



NEW CATECHISM OF ELECTRICITY. 



ELECTRO-MAGNETIC INDUCTION. 

upon which there is no electric current, or a much weaker 
current, the strongly-charged wire excites in the weaker wire 
a sympathetic current, which moves in the opposite direction, 
but vibrates, pulsates, and in all respects reproduces the mani- 
festation of the current in the stronger wire. This is induc- 
tion. The distance at which it will be produced varies with 
the intensity of the current, the atmosphere and the size of 
the wire. 

An understanding of what is meant by induction is abso- 
lutely necessary to the explanation of the alternating system 
of incandescent lighting. In many instances of incandescent 
lighting the wires from the generating plant are carried to the 
outside only of the buildings to be lighted. There they are 
placed in a coil, in close proximity to, but not in contact with ; 
another coil wire leading into the building. From the last- 
named coil, called the ' induction coil, ' wires are carried to 
the glass bulbs, which we see on every hand, in which a. e 
placed carbonized loops. 

Under the alternating system the incandescent lights in 
the buildings are produced, not by the introduction into the 
building of the original current, but by the sympathetic or 
induced current described above, set up in the induction coil 
from the passage of the direct current on the wire and coil 
outside the building. 

This influence, whatever its nature, by which the primary 
induces a current in a secondary circuit is not affected by the 
nterposition of any sheet of material which is non-magnetic 



NEW CATECHISM OF ELECTRICITY. 



ELECTROMAGNETIC INDUCTION. 

and non-conducting. A wooden board, or a sheet of card- 
board, or a sheet of india-rubber, does not 'prevent [the induc- 
tion ; but a thick'sheet of copper greatly diminishes the effect^ 
and a plate of iron prevents it altogether. 

Induction can occur only when the electrified body is 
insolated and it is impossible to insulate against it. 



Fig. 88. 




Electricity Bound. 



8$ 



NEW CATECHISM OF ELECTRICITY. 



Fig. 39. 




Tower Wagon. 



: 



NEW CATECHISM OF ELECTRICITY. §? 



ELECTRICAL RESISTANCE. 



Resistance is that which stops the flow of electricity. 

The practical electrician has to measure electrical resist- 
ances, electro-motive forces, and the capacities of condensers. 
Each of these several quantities is measured' by comparison 
with ascertained standards, the particular methods of compari- 
son varying however, to meet the circumstances of the case. 

Ohm's law shows us that the strength of a current due to 
an electro-motive force falls off in proportion as the resistance 
in the circuit increases. It is therefore possible to compare 
two resistances with one another by finding out in what pro- 
portion each of them will cause the current of a constant 
battery to fall off. 

Silver is taken as the standard, with the percentage of ioo 
and the conductivity of all other metals is expressed in 
hundredths of the conductivity of silver. 



Note. — A current of electricity always flows in a conducting circuit 
when its ends are kept at different potentials, in the same way that a 
current of water always flows in a pipe when a certain pressure of water 
is supplied. The same electrical pressure does not, however, always pro- 
duce a current of electricity of the same strength, nor does a certain 
pressure of water always produce a current of water of the same volume 
or quantity. In both cases the strength or volume of the currents is 
dependent not only upon the pressures applied, but also upon the 
resistance which the conducting circuit offers to the flow in the case of 
electricity, and on the friction (which may be expressed as resistance) 
which the pipe offers to the flow in the case of water. 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL RESISTANCE. 

The metals in general conduct well, hence their resistance is 
small, but metal wires must not be too thin or too long, or 
they will resist too much, and permit only a feeble current to 
pass through them. The liquids in the battery do not con- 
duct nearly so well as the metals, and different liquids have 
different resistances. Pure water will hardly conduct at all, 
except for high potential electricity it is a fair conductor. 

Salt and saltpetre dissolved in water are good conductors, 
and so are dilute acids, though strong sulphuric acid is a bad 
conductor. Gases are bad conductors. 

Another very important fact concerning the resistance of 
conductors is, that the resistance of conductors in general 
increases with the temperature. While this fact is true regard- 
ing metals, with non-metals it is not true. The resistance of 
different metals does not increase in the same proportion. 
Iron at ioo degrees C, has lost 39 per cent of the conducting 
power it possessed at zero, while silver loses but 23 per cent. 

It should be borne in mind that it is not really known what 
produces the quality of resistance any more than we really 
know the laws which govern the transmission of light and 
heat. 

Laws of Electrical Resistance — Resistances in a circuit 
may be of two kinds— -first, the resistances of the conductors 
themselves ; second, the resistance due to imperfect contact at 
points. The latter kind of resistance is affected by pressure, 
for when the surfaces of two conductors are brought into more 
intimate contact with one another, the current passes more 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL RESISTANCE. 

freely from one conductor to the other. The contact-resist- 
ance of two copper conductors may vary from infinity down 
to a small fraction, according to the pressure. The following 
are the laws of the resistance of conductors : 

i. The resistance of a conducting wire is proportional to its 
length. If the resistance of a mile of telegraph wire be 13 
ohms, that of fifty miles will be 50 X 13 = 650 ohms. 

2. The resistance of a conducting wire is inversely propor- 
tional to the area of its cross section , and therefore iu the usual 
round wires is inversely proportional to the square of its 
diameter. Ordinary telegraph wire is about- Jth of an inch 
thick ; a wire twice as thick would conduct four times as well, 
having four times the area of cross section ; hence an equal 
length of it would have only %t\i the resistance. 

3. The resistance of a conducting wire of given length and 
thickness depends upon the material of which it is made — that 
is to say, upon the specific resistance of the material. 

Fig. 40. 




Gi^obb Strain Insulator. 



9° 



NEW CATECHISM OF ELECTRICITY. 



Fig. 41. 




Cabi y e Supporter. 



NEW CATECHISM OF ELECTRICITY. gi 



CONDUCTORS AND NON-CONDUCTORS. 



The manner in which electricity is communicated from one 
body to another depends on the conducting property of the 
body imparting and the body receiving it. 

Bodies differ from each other in a striking manner in the 
freedom with which the electric current moves upon them. 
If the electric current be imparted to a certain portion of the 
surface of glass or wax, it will be confined strictly to that 
portion of the surface which originally receives it, by contact 
with the source of electricity ; but if it be in like manner im- 
parted to a portion of the surface of a metallic body, it will 
instantaneously diffuse itself uniformly over the entire extent 
of such metallic surface, exactly as water would spread itself 
uniformly over a level surface on which it is poured. 



Note.— The discovery of this property of matter is due to Stephen 
Gray, who, in 1729, found that a cork, inserted into the end of a rubbed 
glass tube, and even a rod of wood stuck into the cork, possessed the 
power of attacking light bodies. He found, similarly, that metallic wire 
and pack-thread conducted electricity, while silk did not. 

Gray even succeeded in transmitting a charge of electricity through a 
hempen thread over 700 feet long, suspended on silken loops. A little 
later, Du Fay succeeded in sending electricity to no less a distance than 
1,256 feet through a moistened thread, thus proving the conducting power 
of moisture. From that time the classification of bodies into conductors 
and insulators has been observed. 



92 NEW CATECHISM OF ELECTRICITY. 

CONDUCTORS AND NON-CONDUCTORS. 

The former class of bodies, which do not give free motion 
to the electric fluid on their surface, are called non-conduct- 
ors ; and the latter, on which unlimited freedom of motion 
prevails, are called conductors. 

Of all bodies, the most perfect conductors are the metals. 
These bodies transmit electricity almost instantaneously, 
without any sensible obstruction, provided their dimensions 
are not too small in relation to the quantity of electricity im- 
parted to them. 

Good non-conductors are also called insolators, but it will 
be apparent from what has been explained, that it would be 
more correct to designate bodies as good and bad conductors 
in various degrees, than as conductors or non-conductors. 
There exists no body which, strictly speaking, is either an ab- 
solute conductor or absolute non-conductor. 

The bodies named in the following series possess the con- 
ducting power in different degrees in the order in which they 
stand, the most perfect conductor being first, and the most 
perfect non-conductor last in the list. 



Note.— There are two apparent exceptions to the law that electricity 
resides only on the outside of conductors : (i.) If there are electrified in- 
sulated bodies actually placed inside the hollow conductor, the presence 
of these electrified bodies acts inductively and attracts the opposite kind 
of electricity to the inner side of the hollow conductor. (2.) When elec- 
tricity flows in a current, it flows through the substance of the conductor. 
The law is limited, therefore, to electricity at rest— that is, to statical 
charges. 



NEW CATECHISM OF ELECTRICITY. 



93 



CONDUCTORS AND NON-CONDUCTORS. 

Silver, 



Good Conductors. 



Partial Conductors. 



1 



Copper, 
Other metal, 
Charcoal, 
Water, 
The body, 
Cotton, 
Dry Wood, 
Marble, 
Paper, 

Oils, . 

Porcelain, 

Wool, 

Silk, . 

Resin, 

Gutta-percha 

Shellac, 

pbonite, 

Parraffin, 

Glass, 

Dry air, 

The earth is a good conductor; much difficulty is frequently 
experienced by the wires making contact with some substance 
that will conduct the electricity to the earth. This is called 
" grounding.' y 



Non-Conductors or 
Insulators 



Note. — Copper is preeminently the metal used for electric conduction, 
being at once among the best conductors, the most ductile, the strongest 
and the cheapest ; in each of these respects it is excelled by one or more 
of the other metals, but no other approaches it in the average of all 
qualities. 



94 NEW CATECHISM OF ELECTRICITY. 

CONDUCTORS AND NON-CONDUCTORS. 

Electricity is transmitted, not like light and heat, through 
the interior dimensions of bodies, but only on their surfaces. 
This is proved by the fact that it is found to. be immaterial to 
the distribution what the interior of a conductor is made of ; 
it may be solid metal, or hollow, or even consist of wood cov- 
ered with tin-foil or gilt, but, if the shape be the same, the 
charge will distribute itself precisely in the same manner over 
the surface. There are several ways of proving by direct ex- 
periment this very important fact. 

Glass which is an almost perfect conductor of light, is a 
non-conductor of heat and electricity. Sealing wax, which 
is a non-conductor of electricity, is also a non-conductor of 
light and heat. The metals, on the other, hand, are conduct- 
ors of heat and electricity, but are non-conductors of light. 
Water is a conductor of electricity and light, but a non-con- 
ductor of heat. 

The conducting power of bodies is affected in different ways 
by their temperature. In the metals it is diminished by ele- 
vation of temperature ; but in all other bodies, and especially 
in liquids, it is augmented. Some substances, which are non- 
conductors in the solid state become conductors when fused. 
Sir. H. Davy found that glass raised to a red heat became a 
conductor ; and that sealing-wax, pitch, amber, shell-lac, sul- 
phur, and wax, became conductors when liquefied by heat. 

If a conducting body which is insulated and charged with 
electricity, be brought into contact with another conducting 
body, which is also insulated and in its natural state, the elec- 



NEW CATECHISM OF ELECTRICITY. 95 

CONDUCTORS AND NON-CONDUCTORS. 

tricity will diffuse itself over the surfaces of both conductors 
in proportion to their relative magnitudes. 

The most perfect non-conductors lose their virtue if their 
surface be moist, the electricity passing by the conducting 
power of the moisture. This circumstance also shows why it 
is necessary to dry previously the bodies on which it is desired 
to develop electricity by friction. 

Atmospheric air must manifestly belong to the class of non- 
due tors, for if it gave a free passage to electricity, the electri- 
cal effects excited on the surface of any body surrounded with 
it would soon pass away ; and no electrical phenomena of a 
permanent nature could be produced, unless the bodies were 
removed from the contact of the air. 

Air, however, when rarefied, loses in a great degree its non- 
conducting property ; and an electrified body soon loses its 
electricity when placed in the exhausted receiver of an air- 
pump. 

Water, whether in the liquid or vaporous form, is a conduct- 
or, though of an order greatly inferior to the metals. This 
fact is of great importance in electrical phenomena. The at- 
mosphere, contains suspended in it, always more or less aque- 
ous vapor, the presence of which impairs its non-conducting 
property. 

If a current of electricity pass over a conductor, no change 
in the heat condition of the conductor will be observed so 
long as its transverse section is so considerable as to leave 
sufficient space for the free passage of the current. But, if its 



96 NEW CATECHISM OF ELECTRICITY. 

CONDUCTORS AND NON-CONDUCTORS. 

thickness be diminished, or the quantity of electricity passing 
over it be augmented, or, in general, if the ratio of the elec- 
tricity to the magnitude of the space afforded to it be in- 
creased, the conductor will be found to undergo an elevation 
of temperature, which will be greater the greater the quantity 
of the electricity and the less the space supplied for its pass- 
age. 

These heat effects are manifested in different degrees in 
different metals, according to their varying conducting pow- 
ers. The worst conductors of electricity, such as platinum 
and iron, suffer much greater changes of temperature by the 
same charge than the best conductors, such as gold and cop- 
per. The charge of electricity, which only elevates the tem- 
perature of one conductor, will sometimes render another in- 
candescent, and will vaporize a third. 

The better the conducting power of a substance, the lower 
its electrical resistance, on the other hand the lower its con- 
ducting power the more its electrical resistance. A very small 
percentage of carbon, zinc, iron or other impurity greatly re- 
duces the conducting power of copper, even to one-half. 

Iron is frequently used for conductors. This is owing to 
its comparative cheapness. 

In case of wires, or other conductors, passing through walls, 
etc., they must be covered with a layer of coating of cotton or 
silk, wrapped or braided over the wire. 

When wires or cables are to be used under water, they must 
be made impervious, and great care must be used to prevent 



■I 



NEW CATECHISM OF ELECTRICITY. 



97 



' CONDUCTORS AND NON-CONDUCTORS. 

the water from penetrating and thus injuring the insolation — 
the insulating material must possess a good degree of non- 
conducting power. 

It would be a wise plan, and should always be required, 
that where there is any considerable investment in copper to 
have submitted by the manufacturer a sample piece of fixed 
dimensions which can be tested for its conductivity and where 
it is used for overhead conductors also tested for tensile 
strength. There are a number of processes used in the pro- 
duction of copper which do not eliminate from the copper 
those impurities which seriously affect its resistivity. They 
are not apparent from anything but a test. 



Fig. 42. 




Sub-Marine Cable:. 



9 S 



NEW CATECHISM OF ELECTRICITY. 



Fig. 43. 




TO IUJJSTRATK ARC RIGHTING, 



New catechism of electricity. 99 



ELECTRICAL MEASUREMENTS, 



Klectricity has been termed the science of measurements, 
and 

The electrical industry, more than any other, necessitates 
accurate and varied measurements. Fortunately, the average 
engineer and electrician may quite readily acquire the knowl- 
edge and skill to make all ordinary tests that are necessary, 
and the cost of needful apparatus is not excessive. 

Measurement has been defined as the determination of the 
value of quantities. 

Kvery system of measurement is based upon some experi- 
mental fact or law. An electric current can (1) cause a de- 
position of metals from their chemical solutions ; (2) heat the 
wire that it flows through ; (3) attract (or repel) a parallel 
neighboring current ; (4) accumulate as an electric charge that 



Note— Scales are now made of such a nice adjustment that they will 
weigh anything, to the smallest hair plucked from the eyebrow. They are 
triumphs of mechanism, and are enclosed in glass cases. Two pieces of 
paper of equal weight put in the scales, and an autograph written in pen- 
cil on either piece will cause the other side to ascend, and the needle 
which indicates the division of weight even to the ten millionth part of a 
pound and less will move from its perpendicular. A signature containing 
nine letters has been weighed and proved to be the fifteen thousand five 
hundredth part of an ounce, troy. — Practical Engineer, London^ Fng. 



100 NEW CATECHISM OF ELECTRICITY. 

ELECTRICAL MEASUREMENTS. 

can repel (or attract) a neighboring charge of eletricity ; (5) 
produce in its neighborhood a magnetic field, that is to say, can 
exert a force upon the pole of a magnet placed near it, as, for 
example, in galvanometers ; the fifth of them is made the 
basis in the system now adopted by international agreement ; 
and it is the best because, firstly, it connects the electrical 
units with the magnetic ones, and, secondly, it is closely con- 
nected with the mechanical units, enabling the mechanical 
values of the electrical quantities to be readily computed. 

Instruments for measuring currents of electricity are of 
many styles. As a mysterious and invisible element is dealt 
with, the measurement is indirect. The effects of currents of 
various pressures and volumes are what are measured, not the 
currents themselves. 



Note.— One of the most sensitive instruments to the effect of the cur- 
rent is the ordinary compass needle. Now if a wire through which an 
electric current is passing be laid directly above the needle and parallel 
to it the needle is turned aside from its north and south position. If the 
current flows in one direction the needle will turn to the right. If the 
current is from the other direction it will turn to the left. 

When the current in the wire is very feeble the needle will be de- 
flected very little from its natural position. If the current be very heavy 
the needle will be turned aside much more. In order to effect the needle 
with very small currents the influence must be increased and this is done 
by winding a hollow, flat coil about a space large enough to contain the 
needle. This gives many turns of wire above and below the needle and 
the effect upon the needle is multiplied in proportion to the number of 
turns. 

Upon this principle depends the working of the galvanometer, the 
voltmeter and ammeter. All are.constructed upon the same principle but 
the voltmeter usually has many turns of very fine wire while the am- 
meter has but a few turns of very heavy wire. 



NEW CATECHISM OF ELECTRICITY. 



IOI 



Fig. 44. 



ELECTRICAL MEASUREMENTS. 

If water could be neither seen nor felt we should have to 
determine its volume and height of fall by the effects of the 
stream upon various sizes of waterwheels, the effect of steam 
pressure upon a piston, etc. 

With the growth of electrical science many specially de- 
signed instruments for measurments of electricity have been 
placed upon the market ; almost the first was 

The Galvanometer^ which is chiefly used to measure battery 
currents. A galvanometer must fulfil 
the essential condition that its readings 
shall really measure the strength of the 
current in some certain way. It should 
also be sufficiently sensitive for the cur- 
rents that are to be measured to affect 
it. The galvanometer adapted for 
measuring very small currents (say a 
current of only one or two millionth 
parts of an ampere) will not be suitable 
for measuring very strong currents, such 
as are used in producing an electric light. 
Moreover, if the current to be measured 
has already passed through a circuit of great resistance (as, 
for example, some miles of telegraph wire), a galvanometer 




TH3 
GALVANOMETER. 



Note.— Strong currents must not be passed through very sensitive 
galvanometers, for, even if they are not spoiled, the deflections of the 
needle will be too large to give accurate measurements. In such cases 
the galvanometer is used with a shunt, or coil of wire arranged so that 
the greater part of the current shall flow through it, and pass the galvano- 
meter by, only a small portion of the current actually traversing the coils 
of the instrument. 



102 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL MEASUREMENTS. 

whose coil is a short one, consisting only of a few turns of 
wire will be of no use. 

The Galvaniscope is an instrument used for ascertaining 
whether a current is flowing cr not. It is an indicator of cur- 
rents where the movement of the needle shows the direction 
of the current, and indicates whether it is a strong or a weak 
one. When the value of the readings have been determined 
by experiment or calculation any galvaniscope becomes a 
galvanimeter. 

Fig. 45. 




THE ELECTROSCOPE. 



Note. — The Henly quadrant electroscope is sometimes employed as 
an indicator for large charge3 of electricity. It consists of a pith ball at 
the end of a light arm fixed on a pivot to an upright. When the whole is 
electrified the pith ball is repelled from the upright and flies out at an an- 
gle indicated on a graduated scale or quadrant behind it. The device 
shown in Fig. 45 illustrates the same principle of "electric repulsion." 



NEW CATECHISM OF ELECTRICITY. IO3 

ELECTRICAL MEASUREMENTS. 

The Electroscope is an instrument for detecting whether a 
body is electrified or not and indicating also whether the elec- 
trification is positive or not, The earliest electroscope devised 
consists of a stiff straw balanced lightly upon a sharp point ; 
a thin strip of brass or wood, or even a goose quill, balanced 
upon a sewing needle, will serve equally well. When an 
electrified body is held near the electroscope it is attracted 
and turned round, and will thus indicate the' presence of 
electricity. 

There are many forms of the electroscope, notable among 
which are: i. The Pith Ball ; 2. The Gold Leaf; 3. The Con- 
densing ; 4. Bennett's ; 5. Bohenberger's. Care must be used 
not to confuse the idea of the electroscope, which only indi 
cates the presence, with the following : 

The Electrometer is an instrument for use in measurement 
of potential difference by the attraction of bodies charged with 
static electricity. 

The " quadrant electrometer" designed by Lord Kelvin 
is sometimes made very sensitive so as to measure as low as 
T0V0 volt, but it is a very delicate laboratory instrument. It 
is valuable for measuring differences of potential where no 
current is flowing or where current is undesirable. 

The Mirror Galvanometer. — When a galvanometer of 
great delicacy is needed, the moving parts must be made very 
light and small. To watch the movements of a very small 
needle an index of some kind must be used, indeed, in the 



104 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL MEASUREMENTS. 

tangent galvanometer, it is usual to fasten to the short stout 
needle a delicate stiff pointer of aluminum. A far better 
method is to fasten to the needle a very light mirror of 
silvered glass, by means of which a beam of light can be 
reflected on to a scale, so that every slightest motion of the 
needle is magnified and made apparent. The mirror gal- 
vanometers devised by Sir W. Thomson for signalling through 
submarine cables, are admirable examples of this class of 
instrument. 

Fig. 46, 




THE BATTERY GAUGE. 

Fig. 46 represents a form of portable galvanometer, suita- 
ble for ordinary testing. 



>NEW CATECHISM OF ELECTRICITY. I05 

ELECTRICAL MEASUREMENTS. 

Measurement of electric pressure and current volume. 

The foregoing described instruments belong rather to the 
experimental and testing departments of electrical science, 
but the introduction of the dynamo and motor, with their 
powerful currents have demanded other instruments of greater 
range and capacity. This has caused the development of in- 
struments for measuring 
The Volt. 

The Ampere. 

The Ohm. 

The Volt is the practical unit of measurement of pressure. 

The Ampere is the practical unit of measurement of rate of 
flow. 

The Ohm is the practical unit of measurement of resistance. 

An Ammeter or ampere meter is a device for measuring 
the number of amperes which are passing through a current 
and showing the same by direct reading on a scale. 

The ammeter is a commercial form of galvanometer in 
which the deflections (or twistings) of a magnetic needle are 
valued in amperes. 

Ammeters are made in various forms based upon several 
different principles, among which are 

1. Permanent-magnet ammeters. 

2. Blectro-magnet ammeters. 

3. Spring ammeters. 

4. Gravity ammeters. 



io6 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL MEASUREMENTS. 

Fig. 47. 




THE AMMETER. 



Fig. 48. 




THE VOLT METER. 



NEW CATECHISM OF ELECTRICITY. 



I07 



ELECTRICAL MEASUREMENTS. 

When electric motive force of one volt passes through a 
resistance of one ohm it produces one ampere, hence an am- 
pere is a combination of two things, electric motor force and 
resistance. An ampere will do a certain amount of work, 
will decompose a given weight of water, and will deposit 
.005084 grain of copper per second and in several ways it may 
be demonstrated what an ampere is. An ampere measurer is 
just as necessary to all constant current circuits as is a steam 
guage to a steam plant. 

Fig. 49. 




STATION AMMETER. 



Some ammeters are designed to be used only for standards 
of comparison and others are intended and so constructed that 
they can remain continuously in circuit. Each instrument, 
if well constructed, has considerable range. See Fig. 47. 



IOS NEW CATECHISM OF ELECTRICITY. 

ELECTRICAL MEASUREMENTS. 

The Voltmeter is shown in Fig, 48. It is different from the 
ammeter in having high resistance and is connected between 
the two poles or positive and negative wires. The voltmeter 
measures electric pressure just as the steam guage measures 
the pressure of steam. In the illustration two scales are 
shown, the outside one indicating volts and the inner scale 
one-twentieth of a volt. 

Fig. 50. 




THE) WATT METEJR. 
(i-5th Actual Size.) 

An instrument that will measure accurately from 1 to 100 
volts will not give good results for measuring potentials of 
1,000 to 5,000 volts. An ammeter that will measure accur- 
ately the thousandths of amperes in the current of an indue- 



NEW CATECHISM OF ELrCTRICITY. ICQ 

ELECTRICAL MEASUREMENTS. 

tion coil, will not do at all for measuring ioo or 1,000 am- 
peres. Fig. 47 shows the standard ammeter and Fig. 49 in- 
. strument for use to indicate large station output of electricity. 

The Station Meter. — Electric energy is now supplied in 
large quantities and distributed for lighting, motive power 
and heating from large central stations or power-houses. 
From the power-house distributing mains of copper go out 
consisting of " feeders" leading into the network of con- 
ductors. The station meter, illustrated in Fig. 49, is designed 
to indicate with extreme accuracy the large units being con- 
stantly produced and utilized. 

The Watt Meter. — The watt is an electric unit obtained by 
multiplying the volt, which represents pressure, into the am- 
pere, which represents volume ; hence, a meter designed to 
measure electricity sold to customers for motors, lamps and 
heaters is called a watt-meter or measurer and is illustrated in 
Fig. 50. 

The watt- meter consists of two coils of insulated wire, one 
fine and one coax-se, so arranged in the electric circuit that they 
act upon each other. These produce a motion in a train of 
clockwork by which the electric energy is recorded on dials 
in the same manner as gas consumption is recorded in a gas 
meter. This record is made in watt hours, being 1 volt X 1 
ampere X 1 hour = one watt hour. 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL MEASUREMENTS. 



Fig. 51. 




THE EDISON METER. 



Note.— This is a chemical meter, the amount of chemical action being 
proportioned to the ampere hours. 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL MEASUREMENTS. 

The Edison Meter is shown in Fig. 51. A glass bottle 
contains two zinc plates, immersed in a standardized solution 
of sulphate of zinc. The electric current enters the bottle 
from the terminal of one plate, passes through the solution 
and goes out through the terminal of the other plate. In so 
doing it disintegrates from the "losing plate" particles of 
zinc and deposits on the " gaining plate " their exact equiva- 
lent. The amonnt thus transferred is in exact proportion to 
the amount of current passing through the bottle, according 
to a well-known physical law. The quantity of current 
shunted through the bottle is a definite proportion of the 
quantity going directly into the house, " resistances " within 
the meter fixing the exact proportions. The exactness of this 
proportion is verified before the meter is placed on the system, 
and can be checked at any time by electrical tests on the con- 
sumer's premises. 

Kach three wire meter contains two pairs of bottles, one 
pair on the positive, the other on the negative side of the 
system. The same amount of current passes through each 
bottle of the pair and by weighing the " gaining plate " in one 
bottle and the " losing plate ' ' in the other, a double check 
is obtained. 



Note. — After a meter is installed on a customer's premises it is then 
sealed until the next round of the "meter- wagon." The company's 
representative unseals the meter, removes the bottles, replacing them by- 
others whose plate-weights have been carefully recorded, and brings the 
four bottles in a four-part box back to the Meter Department. Each 
meter has its proper number ; each bottle-box has an identifying label 
which bears the record of the bottle-changing and meter-inspection ; and 
the plates within the bottles are also specifically numbered. 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL RESISTANCE. 

Measurements of Resistance. — Unlike the frictional resist- 
ance of water in pipes, the frictional resistance of the wire is 
readily computed and measured, making the discussion of the 
internal action of the electric system much simpler than one 
of the hydraulic system would be. In fact, we may measure 
the resistance power in a certain definite unit. 

The resistances of wires and circuits are measured in prac- 
tice by comparing them with certain standard "resistance 
coils," sets of which are often employed arranged in "resist- 
ance boxes ; " the particular instruments employed in making 
the comparison being of two kinds, namely, the differential 
galvanometers and the Wheatstone's bridge. 

These resistance coils require great accuracy in their 
measurement, in the insulation of the wire and in the mount- 
ing of the coils. The wires must be carefully selected and 
tested. The insulation must be such as will withstand the 
highest temperature to which it is subjected without change. 
Silk thread is extensively used for the insulation. The wire 
is usually wound on spools or in coils so as to occupy as little 
room as possible, and are mounted in a box, which protects 
them from injury and places them in convenient form to be 
carried. 

The ends of the coils are connected to plates or binding 
posts in the cover. This, also, must be carefully constructed 
so that the resistance at the point of conract will be as low as 
possible. A single coil is sometimes placed in an ebony case, 
or any number, according as the work for which it is to be 
used seems to require. When a large number is placed in one 



NEW CATECHISM OF ELECTRICITY. 



113 



ELECTRICAL RESISTANCE. 

box the ends of the wires are usually connected to metal 
blocks, placed at such a distance apart that a metal plug will 
make a good connection between any two. The resistance 
coils being uniform in size, the entire resistance or any part 
may be used. 

The Mariner's Compass. — The practical interest of mag- 
netism (electricity) applied to navigation need not be en- 
larged upon. The mariner's compass usually consists of a flat 
circular card, on the under surface of which are secured four 
to eight light magnetic needles. The card swings in a " com- 
pass-box " ona pivot placed at its centre, the box having a 
pointer corresponding to the direction of the ship's head — the 
box is supported on gimbols — an arrangement for preserving 
it horizontal while the ship is pitching and tossing. The card 
is divided into thirty-two points by a star engraved on it, Fig. 
52, and it is by these points the course is steered. 

Fig. 52. 
N 




THE MARINER'S COMPASS. 



114 NEW CATECHISM OF ELECTRICITY. 



SYMBOLS, ABBREVIATIONS AND 
DEFINITIONS. 



It is well for the reader to memorize the following ques- 
tions and answers in the same way that the letters of the 
alphabet or the multiplication are committed to memory, as 
more or less of them are used upon every page of printed 
matter relating to electricity. 

QuKS. What is the meaning of the letters E. M. F. ? 

Ans. Electro-motive force (abbreviated K. M. F.) is the 
name given to the force or cause which produces an electric 
current, see page 45. 

The fundamental property of matter is, that it cannot 
impart motion to itself. The inability of matter to put itself 
in motion is called inertia — that which causes motion is force 
and that which causes the electric current is electro-motive 
force (K. M. F.) 

Ouks. What are the '''-powers of ten " ? 

ANvS. This system of notation is sometimes called " Index 
Notation.' ' This consists in using some power of ten as a 
multiplier in order to avoid the use of long rows of cyphers. 



NEW CATECHISM OF ELECTRICITY. 115 

SYMBOLS, ABBREYIATrONS AND DEFINITIONS. 

The following examples will show the convenience of the 
system. The resistance of selenium is about 40,000,000,000, or 
4 X io 10 times as great as that of copper ; that of air is about 
io 36 , or 

1 00 , 000 , 000, 000 , 000, 000 , 000, 000, 000 
times as great. The velocity of light is about 30,000,000,000 
centimetres per second, or 3 X io 10 times. 

OuKS. What is the C. G. S. system of notation ? 

Ans. The C. G. S. unit represents the work of a body 
equal in weight to one gramme, through a space equal to one 
centimetre in one second. This is the absolute or fundamental 
unit of electrical work or energy and denominated an erg. 

QuKS. What is the definition of function ? 

Ans. This word is derived from a Latin word meaning to 
perform— hence its general sense is "performance." 



Note. — The system of units adopted by almost universal consent is 
the so-called " Centimetre-Gramme-Second " system, in which the funda- 
mental units are : 

The Centimetre as a unit of length ; 
The Gramme as a unit of mass ; 
The Second as a unit of time. 
The Centimetre is equal to 0.3937 inch in length. 
The Gramme is equal to is.ttto or grains. 
The Second is i-6oth of one minute. 

All physical quantities, such as electricity, force, velocity, etc., can be 
expressed in terms of these fundament at quantities : length, mass, and 
time. Each of these quantities must be measured in terms of its own 
units. 



Il6 NEW CATECHISM OF ELECTRICITY. 

SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

Ques. What is an ohm ? 

Ans.' An ohm is' the practical unit of electric resistance 
and many researches have been made to determine its work- 
ing value. For a wire of a certain quality the resistance is in 
proportion to the length and also in proportion to the cross 
section or size. 

QuKS. What is Ohm' s taw f t 

Ans. The question of relation between volts, amperes 
and resistance is expressed under one universal law, which is 
known as Ohm's law, c=^ y in which " C " stands for current, 
"E" for electro-motive force or volts, and " R " for resistance. 

Current in amperes equals pressure in volts divided by 
resistance in ohms, or again, electro-motive force equals resist- 
ance multiplied by current ; and again, resistance equals 
electro-motive force divided by the current ; thus it will be 
seen that these terms are dependent upon each other, and that 
their relation to each other is expressed by this law. 

These are written in three wavs : 







K 




I. 


c. 


— R 




2„ 


K. 


= CXR, 
E 


or 


3- 


R. 


— C 





If one volt will force one ampere of current through a cir- 
cuit having one ohm resistance it will take five volts to force 
five amperes through the same circuit. If this resistance 
should be increased to five ohms it would take five times five 



NEW CATECHISM OF ELECTRICITY. 117 

SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

amperes for the proper number of volts to force the amperes 
through, which would be 25 volts. From this it can be seen 
that it is very easy to obtain any one of these quantities when 
we have the other two. 

QuKS. What is a volt ? 

Ans. The volt represents an electric pressure nearly equal 
to that of a Daniel battery cell described page 55 ; it is the 
practical unit of K. M. F. such as may be induced in a con- 
ductor which cuts lines of magnetic force at the rate of one 
hundred millions per second. 

QuES. What is an ampere ? 

Ans. The ampere is the practical unit of electric current 
and represents a volume of a current produced by a pressure 
of one volt flowing through a conductor having a resistance of 
one ohm. 



Ques. What symbol is used to indicate battery cells joined 
up in one row, or as they are said to be " in series." 

Ans * Jiliiilihlk By tlle use of a s y mbo1 ( see cut ) in 

n'lM'rrl'j which a short thick line stands for 
Fig. 53. the zinc and a longer thin line stands 
for the copper (or carbon). Thus V^ig. 53 represents six cells 
joined in series. 

Similar symbols are used for " condensers" in diagrams of 
electric circuits. 



IlS NEW CATECHISM OF ELECTRICITY. 

SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

OuKS. What is meant by reluctance ? 

Ans. The reluctance of a magnetic circuit corresponds 
with the resistance of an electric circuit. 

QuES. What is the meaning of ■ ' coil" f 

Ans. That which is gathered or wound into a ring or 
circle. 

. OuES. What is the definition of i ' laminated ' y ? 

Ans. It means plated — consisting of plates, layers, or 
scales laid one over the other. 

QuKS. What is the definition of ' 'periphery " ? 

Ans. It means the circumference or outside of a circle, 
ellipsis, or other regular curvilinear figure. 

OuKS. What is the definition of the zvord "potential" f 
Ans. This oft-used word means in its primary sense — 

power to do work — in this connection it denotes power to do 

electric work. 

OuKS. What is the definition of ' i shunt ' ' ? 

Ans. This is a contraction of "shun it." In railways a 
turning off to a siding that the principal line of rails may be 
left free — this idea is transferred to electricity literature. 

Ques. What is the definition of calibration ? 
Ans. This word comes from one originally meaning " the 
diameter of a body " and is kindred to the word " calipers." 



i 



NEW CATECHISM OF ELECTRICITY. IIQ 

SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

In electrical literature it means to determine the absolute or 
relative value of the scale divisions or of the indications of any 
electrical instrument, such as a galvanometer, watt-meter, etc. 

QuKS. What is meant by periodicity ? 

Ans. The rate of succession of alternations, or the rate of 
change in the alternations or pulsations of an electric current. 

Qu^s. What is staggering f 

Ans. This term is used when one brush is placed slightly 
in advance of the other brush so as to bridge over a break in 
the circuit of the armature wires. 

QuKS. What is polarity ? 

Ans. Polarity is that quality possessed by a mineral when 
it attracts one pole of a magnetic needle and repels the other. 

OuKS. What is meant by the term "inversely " f 
Ans. This means to turn into a contrary direction — a 
change of order so that the last becomes first. 

QuES. What is meant by permeability ? 

Ans. Permeability is the conductivity for magnetic lines 
of force. In other words, it is a measure of the ease with 
which magnetism passes through any substance. The permea- 
bility of good soft wrought iron is sometimes 3000 times that 
of air, varying with the quality of the iron. 



Note. — The magnetic permeability decreases as the magnetization 
increases. When a piece of iron has been magnetized up to a certain 
intensity its substance shows a tendency to reach magnetic saturation. 
In good iron this is reached at about 125,000 lines of force to the square 
inch of area of cross section. 



NEW CATECHISM OF ELECTRICITY. 



SYMBOLS, ABBREVIATIONS AND DEFINITIONS, 

QuES. What is the air gap ? 

Ans. A name given to the part of the magnetic circuit 
composed of air. Usually the air gap is between the pole 
pieces and the iron core of the armature. More or less air gap 
is necessary to provide room for the armature wires and also 
for mechanical clearance between armature and pole pieces. 

QUKS. What is the output of a dynamo ? 

Ans. By the output of a dynamo is meant the electrical 
activity of the machine in watts, as measured at its terminals; 
or, in other words, the output is all the available electrical 
energy. 

Quks. What is the intake of a dynamo f 
Ans. The intake of a dynamo is the mechanical activity 
it absorbs, measured in watts. 

Quks. What is ' ' torque ' ' t 

Ans. This is the force which produces the motion around 
a shaft or axis. It is often expressed as the pounds of " pull ' ' 
excited at the end of a lever arm one foot long. An example 
is the "pulling " or turning force of an armature of an electric 
motor, on its shaft. 

Quks. What is the definition of "electrical efficiency ' " ? 

Ans. In a dynamo or generator the relation of total elec- 
tric energy produced, to the useful, or available electrical 
energy, thus : if a machine produced but half the work repre- 
sented by the energy it absorbed, the rest disappearing in 



NEW CATECHISM OF ELECTRICITY. 121 



SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

wasteful expenditure — in heating the bearings — in overcoming 
the resistance of the air, etc., its efficiency would be expressed 
by Yz or " fifty per cent." 

Ques. What is a watt ? 

Ans. This is the unit of electric power, or the T j ¥ of a 
horse power. It expresses the quantity of work per second, 
done in any electrical resistance. It is the volt-ampere. 

QuKS. What is a kilo-watt ? 

Ans. The name is given to 1,000 watts. One kilo- watt is 
slightly more than i l /£ horse-power. Kx. — A dynamo of 20 
units, or a 20 unit machine, is one capable of giving an output 
of 20 kilo-watts. 

QUES. What is a mil? 

Ans. A mil is one-thousandth part of a lineal inch. It is 
equal to .025399 millimeter. 

.000083 °f a foot. 
.001000 of an inch. 
A mil is a unit of length. 

QUKS. What is a circular mil? 

Ans. A unit of area ; employed in designating the cross- 
sectional area of wires and other circular conductors. 

It is equal to .78540 of a square mil. 

If the diameter of a wire is given in mils the square of its 
diameter gives its cross-sectional area in circular mils. 



NEW CATECHISM OF ELECTRICITY. 



Fig. 54. 




THK INDIANAPOLIS MACHINE, 



NEW CATECHISM OF ELECTRICITY. 1 23 



THE DYNAMO. 



The word dynamo, meaning power, is one transferred from 
the Greek to the English language, hence the primary mean- 
ing of the term signifying the electric generator is the electric 
power machine. 

The word generator, too, is also derived from a word 
meaning birth-giving, hence also the dynamo is the machine 
generating or giving birth to electricity. 

Again, the dynamo is a machine driven by power, generally 
steam or water power, and connecting the mechanical energy 
expended in driving it into electrical energy of the current 
form. 



Note. — It should be understood that an electric dynamo or battery does 
not generate electricity, for if it were only the quantity of electricity that is 
desired, there would be no use for machines, as the earth may be regarded 
as a vast reservoir of electricity of infinite quantity. But electricity in 
quantity without pressure is useless, as in the case of air or water, we can 
get no power without pressure, a flow of currents. As much air or water 
must flow into the pump or blower at one end as flows out at the other. 
So it is with the dynamo ; for proof that the current is not generated in 
the machine, we can measure the current flowing out through one wire, 
and on through the other, it will be found to be precisely the same. As 
in mechanics a pressure is necessary to produce a current of air, so in 
electrical phenomena an electromotive force is necessary to produce a 
current of electricity. A current in either case can not exist without a 
pressure to produce it. 



IL'4 NEW CATECHISM OF ELECTRICITY. 

THE DYNAMO. 

Fartaday's great discovery was made in the autumn of 1831, 
and after various experiments he produced his " new electrical 
machine " shown in Fig. 55. This piece of apparatus is pre- 
served and was shown in perfect action by Prof. S. P. Thomp- 
son in a lecture delivered April nth, 1891, after an interval of 
sixty years. Its operation is as follows : 

1 ' L/et a copper disc be hung on a shaft and so balanced as 
to turn freely. A horse-shoe magnet is so placed that its 

Fig. 55. 




G 

THE) FARRADAY DYNAMO (A. D. 1831.) 

inter polar lines of force traverse the disc from side to side. 
A copper ' i brush ' ' is placed so as to touch the shaft, and one 
to touch the edge of the wheel. A handle serves to rotate the 
wheel in the magnetic field. Now let the wheel be rotated 
clockwise, and if the north pole of the magnet is nearest the 
reader, the result will be to produce a radial current flowing 
out at the brush on the edge and back, through the brush on 
the shaft." 

In Fig. 56 let D show the dynamos in action and let A B 
be a long lead with its farther end to earth. L,et the other 



NEW CATECHISM OF ELECTRICITY. 125 

THE DYNAMO. 

brush or terminal of the dynamo be also connected to earth. 
The dynamo when in action is just like a cistern of water at 
a high level, or a pump ; it urges electricity into the lead 
A B, and at every point a b c in the lead there is a certain 
electric pressure analogous to the water-pressure in the pipe. 
The electricity flows in the lead between any two points a 
and b, in virtue of a difference of electrical pressure between 
these points ; and the flow or quantity per second, or current 
strength, is determined by two things ; this difference of pres- 
sure and the resistance of the piece of lead between the points 
considered. Along the lead there is a regular fall or gradient 
of pressure represented by the sloping dotted lines in lower 
■oart of Fig. 57. 

It may thus be seen that the same laws which control the 
flow of water apply exactly to the electric current. 

Dynamos, are classified into 

1. Unipolar dynamos. 

2. Bi-polar (or 2 poles). 

3. Multipolar dynamos. 

This division is caused by their different construction and 
is treated under the heading * l pole pieces." 

The dynamo is used for three principal purposes. 

1. Incandesent lighting. 

2. Arc lighting. 

3. For distribution of power. 



126 



NEW CATECHISM OF ELECTRICITY. 



THE DYNAMO. 



Fig. 56. 







t : 



4 fr & ■ £ «i e ? jjj"" 



a 



DYNAMO IN ACTION. 





■^ 


1 




Pig. 


57. 




I 


% J 














V 
































.-■=_ --'■€-_ — . - 


"z 


' 




C' 












c 
























-••« 


<£' 










: 




\\ 








e' 










-■\ 








= : 


"* 


f 1 








. 


- 










** 


V' 








Gs 


b 


C 


:<£ 


e 


f 


£_, \ 


J? 


A fc 






r 












^^. 



FLOW OF WATER UNDER PRESSURE, OR HEAD. 



NEW CATECHISM OF ELECTRICITY. 12 7 

THE DYNAMO. 

Its various modifications of size and form are designed to 
meet these, but there is still one other use to which it is put, 
i. e., for experiments which come outside the limit of this 
work. 

When used for power purposes the machine is called a 
generator, /. e. y it generates electricity to be used through 
motors. 

The dynamo in its very simplest form consists of two 
main portions : (i) an armature, which in revolving induces 
electromotive-forces in the copper conductor wound upon it; 
(2) a field-magnet, that is to say a magnet whose function is to 
provide a field of magnetic lines, to be cut by the armature 
conductors as they revolve. In all dynamos, whether for 
.continuous currents or for alternate currents, these two parts 
can be recognized. In almost all continuous-current machines 
the field-magnet stands still, and consists of a comparatively 
simple and massive electromagnet ; whilst the armature, 
which is a more complex structure, is the portion which 
rotates. In alternate-current machines the field-magnet is 
usually multipolar, and in the majority of cases is stationary, 
whilst the armature rotates ; nevertheless there are many 
alternators of recent pattern in which the armature stands 
still and the field-magnet rotates. 

The criterion as to which portion is properly called " field 
magnet,' ' and which " armature," is not the question of rota- 
tion or otherwise. The name of field-magnet is properly given 
to that part which, whether stationary or revolving, maintains 
its magnetism steady during the revolution • and the name 



128 NEW CATECHISM OF ELECTRICITY. 

THE DYNAMO. 

armature is properly given to that part which, whether re- 
volving or fixed, has its magnetism changed in a regularly 
repeated fashion when the machine is in motion. 

In the case of continuous current machines there is another 
feature of first importance, namely, the apparatus for collect- 
ing the currents from the revolving armature. This apparatus 
consists of two essential parts ; the commutator (or collector) 
attached to the armature and revolving with it, and the 
brushes. The latter, which are conducting contact pieces 
held pressed against the surface of the rotating commutator, 
are provided with special brush-holders mounted upon an 
adjustable frame or rocker. 

In the case of alternate-current machines there is no need 
of a commutator ; but, in general, these machines have to be 
provided with some device for making a sliding connection. ■ 
For in those forms in which the armature rotates, its coils 
must be brought into continuous metallic relation with the 
conductors of the main circuit ; and in those forms in which 
the armature is stationary and no such arrangement is needed 
at that part, there must still be sliding contacts to maintain 
the coils of the revolving field-magnet part in continuous 
metallic connection with the auxiliary exciting circuit. In 
either case the appropriate device consists of a pair of collect- 
ing rings, against each of which a brush presses. 

Hence, to summarize, the dynamo-electric generator or the 
dynamo-electric machine, proper, consists of five principal 
parts viz.: 

j. The armature, or revolving, portion. 



.NEW CATECHISM OF ELECTRICITY. 



I2Q 



THE DYNAMO. 

2. The field magnates, which produce the magnetic field 
in w T hich the armature turns. 

3. The pole-pieces. 

4. The commutator or collector. 

5. The collecting-brushes that rest on the commutator 
cylinder and take off the current of electricity generated by 
the machine. 

Fig. 58. 




the: simplest conceivable dynamo. 



The simplest conceivable dynamo is that shown in Fig. 58, 
consisting of a single loop of wire C C, rotating or turning on 
spindle A A between the poles of a large magnet N S. The 
brushes are represented by B B and the electric circuit 
by the line B. The lines of force are represented by the 
dotted lines running between tfye two poles N and S. 



ISO 



NEW CATECHISM OF ELECTRICITY. 



THE DYNAMO. 

Parts of Dynamo. — The nature and uses of the different 
parts of a dynamo will be understood by reference to Fig. 59, 
which represents a complete machine. In this type of dynamo, 
as in the majority of continuous current dynamos, the mag- 
netic field is stationary whilst the armature revolves in it. 

Fig. 59, 




A COMPLETE DYNAMO. 



The magnetic field in the particular dynamo illustrated is pro- 
duced by the iron horse-shoe electro magnet M, which is, 
excited by the current flowing in the magnetizing coils K B. 
The ends or poles of the field magnet M are bored out so as to 
form a circular chamber within which the armature A rotates. 
This latter consists of an iron core rigidly fixed to a steel shaft 



NEW CATECHISM OF ELECTRICITY. 13 1 

THE DYNAMO. 

or spindle S, which revolves in the two bearings F F. Upon 
one end of the shaft is fixed the. driving pulley P. The iron 
core is overwound with a large number of insulated copper 
conductors or coils, the ends of which are connected to the 
circular commutator C. Two stationary metallic brushes, 
B B, press upon the latter, and convey the current generated 
in the coils of the armature through the flexible conductors or 
" leads," L Iv, to the terminals T T, from whence it is con- 
veyed to the external or working circuit. When the machine 
is in action, the armature and conductors or coils are caused 
to rotate within the magnetic field, produced by the electro 
magnet M, by means of a belt passing over the pulley P. In 
consequence, K. M. F.s are induced in the conductors, which, 
on being commutated at the commutator, are transmitted 
through the medium of the brushes and flexible leads to the 
two terminals T T, giving rise to a difference of potential be- 
tween the latter. 

In the classification of dynamos the two principal divisions 
are 

i. Direct current dynamos, and 

2. Alternating dynamos, and in each class there are many 
forms of construction. 

The direct current dynamos are again divided into three 
classes, thus, 

I. Series wound. 

2. Shunt wound. 

3. Compound wound. 



132 



NEW CATECHISM OF ELECTRICITY. 



THE DYNAMO. 

The manner in which the wiring of the fixed magnets are 
connected to the armatures gives rise to the foregoing classifi- 
cation : 

Series Dynamos. — The manner in which the connections 
of the series wound dynamo are arranged is shown in Fig. 60. 

Fig. 60. 




SERIES WOUND DYNAMO* 



The coils of the field magnet are wound with a few turns of thick 
insulated wire, and being joined in series with the armature, 
the whole of the current generated in the latter passes direct 



NEW CATECHISM OF ELECTRICITY. 



133 



THE DYNAMO. 

through them, and thence to the external circuit. The current 
in passing through the coils of the field magnet energizes the 
latter, and creates a magnetic field between the two poles N S, 
in which the armature revolves. 

Fig. 61 




SHUNT WOUND DYNAMO. 



Shunt Wound Dynamos. — The shunt wound dynamo differs 
from the series wound machine, in that an independent circuit 
is used for exciting its field magnet. This circuit is composed 
of a large number of turns of fine insulated copper wire, 



134 NEW CATECHISM OP ELECTRICITY. 

THE DYNAMO. 

which are wound round the field magnet and connected to 
the brushes, so as to form a shunt or ' ' by pass ' ' to the brushes 
and external circuit. Fig. 61 shows the connections of the 
shunt wound dynamo, from which it will be seen that two 
paths are presented to the current as it leaves the armature, 
between which it divides in the inverse ratio of the resistance ; 
whilst one part of the current flows through the magnetizing 
coils, the other portion flows through the external circuit. In 
all well designed shunt dynamos, the resistance of the shunt 
circuit is always very great, as compared with the resistance 
of the armature and external circuit, and the strength of the 
current flowing in the shunt coils rarely exceeds 12 amperes 
in even the largest machines. 

Compound Wound Dynamos. — These are in fact a combina- 
tion of the series wound and the shunt wound machines. 
See Fig. 62. The field magnet of this dynamo is wound 
with two sets of coils, one set being connected in series, 
and the other set in parallel, with the armature and external 
circuit. 

For the purpose of automatically maintaining a constant 
pressure in incandescent lighting the compound wound 
dynamo is now generally employed. 

Separately Excited Dynamos. — This type of machine is not 
so extensively used as the self-exciting type, owing principally 
to the fact that an independent dynamo or battery is necessary 
for exciting its field magnet. It finds its chiefest application 
in the electric transmission of power, and in charging accum- 



NEW CATECHISM OF ELECTRICITY. 



135 



THE DYNAMO. 

ulators, and in all cases where a high E. M. F. is required 
with a varying current. The connections of this dynamo are 
shown in Fig. 63, where N S are the poles of an electro 
magnet which is excited by the current generated by the 

Fig. 62. 




COMPOUND WOUND DYNAMO. 



independent dynamo or battery D. The armature A revolves 
in the space between the two pole pieces, and the two brushes 
B x B 2 press upon the commutator C, and convey the current 
generated in the armature to the external circuit E. The 



136 



NEW CATECHISM OF ELECTRICITY. 



THE DYNAMO. 

E. M. F. and output of the dynamo is usually regulated by 
varying the strength of the magnetizing current (produced by 
the dynamo or battery D) flowing in the coils of the field mag- 
net by means of the hand regulator R. 

Fig. 63. 



*9 AhR <* 




WINDING FOR SEPARATELY EXCITED DYNAMO. 



Note— In the above illustration, as also Figs 60, 61, 62 the external cir- 
cuit is intended to represent a series of lamps in process of receiving the 
current, 



NEW CATECHISM OF ELECTRICITY. 



137 




Fig. 64. 



138 



NEW CATECHISM OF ELECTRICITY. 



THE ARMATURE. 



The armature should always be considered as a cylindrical 
magnet having poles in opposite sides of its periphery, and 
the whole mas 3 of the armature in what is known as the mag- 
netic flux of the field. 

The armature is placed where it will be in the strongest 
magnetic flux and the iron core of the armature acts as a 
stepping stone between the poles of the field. It is because 
of this intermediate mass of iron that the flux is so strong. 

Fig. 65. 




THE EDISON (BAR) ARMATURE. 



Note. — There are several ways of arranging the coils upon the arma- 
ture, and the methods adopted may be classified as follows : — 

:. Drum Armatures, in which the coils are wound longitudinally upon 

the surface of a cylinder or drum. Examples : the Siemens and 

Edison machines. 

2. Ring Armatures, in which the coils are wound around a ring, Ex- 
amples : Gramme and Brush machines. 



NEW CATECHISM OF ELECTRICITY. 1 39 

THE ARMATURE. 

The types of armature in most extensive use at the present 
time are the following : — 

The Ring or Gramme Armature, in. which the coils are 
arranged upon an iron ring. 

The Drum or Siemens Armature, in which the coils are 
arranged upon the surface of an iron cylinder or drum. 




3 

THOMPSON HOUSTON ARMATURE). 

Each of these forms of armature has its special advantages, 
and in a general way it may be said that whilst the ring arma- 
ture is more suitable for generating small currents at high 
potentials, the drum is better adapted for producing moderate 
potentials and large currents. 



NEW CATECHISM OF ELECTRICITY. 



THE ARMATURE. 



Fig. 67. 




THE WESTERN ARMATURE). 



Fig. 68. 




THE WESTERN ARMATURE COMPLETE 



Fig. 




FIG. 69 REPRESENTS THE DISC AS BUII/T UP. 



NEW CATECHISM OF ELECTRICITY. I4I 

THE ARMATURE. 

Fig. 66 shows the drum form of armature (Thompson- 
Houston). 

Fig. 65 shows the drum armature (Kdison). 

Fig. 67 represents the uncompleted form of the drum arma- 
ture and Fig. 68 the same in order for use. 

Fig. 69 represents the toothed core-disk of which drum 
armatures are largely built up. These have two advantages 
over smooth armatures. (1.) The teeth present an excellent 
means of driving the copper conductors which lie between 
them. (2). The teeth may be brought very close to the polar 
surfaces of the field-magnet. 

To set against these real advantages are the disadvantages 
of somewhat greater labor required in milling out the 
channels between the teeth of the assembled core ; the 
extra difficulty of insulating the core from the conductors ; 
and the liability of the teeth to set up eddy-currents in 
the polar faces. The latter can be cured by making the 
teeth numerous and narrow, also by laminating the polar 
faces with grooves, and by enlarging the clearance. Or, best 
of all, by finally serving the entire armature outside the copper 
conductors with a layer of iron wire. Armatures built up of 
toothed core -disks have been much used in recent years, 
particularly for motors. The advantages offered by toothed 
core-disks are possessed to a still higher degree by core-disks 
pierced with apertures, for the purpose of ventilation, just 
within the periphery. 

Fig. 70 represents the ring or gramme armature. The 
arrangement of the lines of force in the magnetic field 



I42 



NEW CATECHISM OF ELECTRICITY. 



THE ARMATURE. 

between the two poles N and S when the ring is inserted 
therein, is shown by dotted lines in the figure. If the arma- 
ture core be rotated in the direction of the arrow, the whole 
of the conductors, being immovably fixed to the armature, 

Fig. 70. 




DIAGRAM OF RING ARMATURK. 



must necessarily partake of the movement. Owing to this 
peculiar arrangement a very intense magnetic field is created 
between the outer surface of the armature core and the pole- 
faces, while the interior space within the core remains almost 
entirely free from lines of force. 



NEW CATECHISM OF ELECTRICITY. 143 

-■=-' . . . , — . 

THE ARMATURE. 

A broad distinction may be set up between wire wound 
armatures and those with built up coils consisting of bars and 
connectors, or of specially constructed portions that are put 
together instead of being wound on. These are classified as: 

1. Wire wound armatures. 

2. Bar armatures. 

Wire-wound armatures are usual for outputs below ioo am- 
peres, including all arc-lighting machines. For armatures 
having outputs exceeding 200 amperes bar-armatures are more 
frequent, owing to the inflexible nature of wires that are 
thick enough to carry these currents. The two classes com- 
prise several varieties as under : — 

Wire-wound Armatures. Bar Armatures. 

Single round wire. Round bars. 

Two or more round wires in Rectangular bars. 

parallel. Rectangular strips. 

Stranded wire. Rectangular bars of corn- 
Single square wire. pressed stranded wire. 

Single rectangular wire. - Special forgings. 

The armatures of alternators may be of ring, drum, pole, 
or disk type ; but in all cases the grouping of the windings is 
different from that which would be adopted for a direct-cur- 
rent dynamo. 

The ring armature is considered the most desirable, 
because it is not so liable to give out ; and if it does, the cost 
of repairing is less than for a drum armature, and the time 
lost on account of the damage is less, as a ring armature may 



144 NEW CATECHISM OF ELECTRICITY. 

THE ARMATURE. 

be put in service as soon as the repairs are made ; and again 
Fig. 76. when an armature short-circuits, it seldom 

O burns out more than two or three coils. If 
it is of the ring type the coils can be readily 
removed and new ones wound in their places, 
and if the workman is sufficiently skilled he 
will not have to disconnect the commutator 
to make the repairs ; therefore, the cost of 
replacing the damaged coils will be small. With a drum 
armature the case is quite different. 

Armature Cores. — The cores of all practical armatures are 
now invariably laminated or constructed of iron wire ribbons 
or disks and are frequently constructed with deep channels or 

Fig. 72. 




TOOTHED CORES. 



grooves in the outer periphery, as shown in Fig. 72, in which 
the conductors are wound. The projections or teeth in this 
method of construction present an excellent means of driving 



NEW CATECHISM OF ELECTRICITY. 



145 



THE ARMATURE. 

and protecting the conductors, but the difficulty of insulating 
the latter from the core is increased by their use, and they 
also have a tendency to produce eddy currents in the pole 
pieces of the field magnets, causing a heating of the latter. 
The latter disadvantage can, however, be obviated to a great 
extent by making the teeth very narrow and numerous. 

In most cases notches or keyways are stamped on the inner 
periphery on the disks as in Fig. 71. 

Fig. 73. 





LAMINATED CORE). 



This core is built up of thin plates of sheet iron of the shape 
shown at B, Fig. 73. Three of them form a perfect ring with 
the teeth projecting from the circumference. Upon the 
inner surface are two hooks which enclose the bolts of the 
spider. In order to break joints the segments are placed over 
alternate spaces. This method of building up the core and 
securing the segments binds the whole firmly together. The 



146 NEW CATECHISM OF ELECTRICITY. 

THE ARMATURE. 

strain is not thrown in the least on the spider, a fact that 
allows the spider to be made of smaller cross sections. 

The winding of the armature is shown at C. It is com- 
posed of four wires of the form shown. This winding is care- 
fully insulated before being placed in the slot of the armature 
core, thus the removal of a coil is an easy matter. The com- 
mutator connection is made by means of screws which pass 
through the connector on the end of the winding. 

Points Relating to the Armature.— -There should be a 
uniform clearance of at lea«t an eighth of an inch all around 
between the armature and the pole pieces. 

They should be perfectly balanced so as to run without 
jar or vibration. 

The essential service of the armature is to rotate in the 
magnetic field, whilst carrying electric currents in its copper 
coils or conductors. 

While in the first place power is required to drive the 
armature, in the second the armature, rotating, becomes a 
source of power. 

Most makers test their armatures for balance by laying the 
journals on two parallel metal rails (or " knife-edges ") and 
noting whether the armature will remain in any position 
without tending to roll. It is well indeed to balance them 
thus on completing the core ready for winding, and again 
after winding. If the end core-disks have been made of thick 
iron, holes can be drilled in these to restore perfect balance ; 
or leaden plugs can be inserted. 



NEW CATECHISM OF ELECTRICITY. 147 

THE ARMATURE. 

After an armature has been wound trie conductors must be 
secured in their place by a number of external bands, known 
as binding wires. These must be very strong, to resist centri- 
fugal force and to hold the conductors from being dragged 
aside ; and yet at the Same time must occupy very little radial 
depth, that the clearance between conductors and pole-face 
may be as narrow as possible. Some makers use hard-drawn 
brass, others phosphor-bronze, others steel, for binding wires. 

Armature cores are usually built up upon an internal frame 
or skeleton pulley firmly keyed to the shaft. In drum arma- 
tures this internal supporting frame may be omitted, the core- 
disks themselves being keyed directly on to the shaft. 

A drum armature should be allowed to stand for several 
days, so that the insulating varnish may become thoroughly 
dry and hard. If the armature is started before it is dry, the 
wires may shift under the strain of centifugal force, and 
furthermore, the liquid in the varnish, in most cases, is of low 
enough resistance to allow the current to break through the 
insulation and burn out the coils, thus rendering it necessary 
to make the repairs over a second time. 

Cores are always laminated, being constructed either of (i) 
sheet iron disks , (2) iron ribbon, or (3) iron wire. Ribbon is 
seldom used. For drums and elongated rings, disks 
stamped out from soft sheet iron are almost universal. The 
usual thickness is from 40 to 80 mils). They should be of the 
softest iron. After being stamped out they should be an- 
nealed, and the burr at the edges removed. Some makers 
at this stage assemble them upon the shaft, turn them down 



I48 NEW CATECHISM OF ELECTRICITY. 

THE ARMATURE. 

truly in the lathe, then take them apart and remove the burr 
by grinding lightly on an emery wheel, then remount them. 
Before being finally mounted on the shaft they must be lightly 
insulated one from the other. For this purpose it is usual 
either to cover one face of each core-disk with varnished 
paper, or to enamel both faces of each core-disk. 

It is usual to make the two end core-disks of stronger iron, 
sometimes as much as X~i ncn thick. 

Wire cores were at one time largely in vogue, having been 
used by Gramme. The soft iron wire, varnished or slightly 
oxidized on its surface, was wound on a special former, then 
removed, taped externally, and wound with the copper wire 
conductors. Wire cores have disadvantages which have 
largely stopped their use. 



OOOO 



NEW CA'ILCHISM Q> ELECTRICITY. 



149 



Fig. 74. 




THE) WKSTINGHOUS3 MACHINE. 



I50 NEW CATECHISM OF ELECTRICITY. 



FIELD MAGNETS. 



The field magnet, the function of which is to produce an 
intense magnetic field within which the armature revolves, 
may be either a permanent magnet or an electro magnet. 
Electro magnets, however, possess such a number of important 
advantages over permanent magnets, that they are now in- 
variably used in all machines intended for practical work. 

The chiefest advantages of the electro magnet, as compared 
with the permanent magnet, lies in the power of regulating 
the strength of the magnetic field produced by the former, by 
suitably adjusting the strength of the magnetizing current 
flowing through its coils, and also in the greater magnetic 
effect obtained, weight for weight, from the electro magnet 
over ihe permanent magnet. 

The field magnets of a dynamo may be excited, either by 
the current furnished by an independent dynamo or battery, 
in which case the machine is said to be " separately excited,' ' 
or by the current generated in the armature of the machine 
of which the field magnet forms part, when the machine is 
said to be self-excited. 

The latter type of machine depends for its action upon the 
presence of residual magnetism in its field magnet. Owing 
to this residual magnetism, a weak magnetic field is always 



NEW CATECHISM OF ELECTRICITY. 151 

FIELD MAGNETS. 

present Between the pole pieces of a field magnet ; hence, 
when the armature is rotated in the armature chamber, its 
conductors cut the lines of force contained in this magnetic 
field, and a small B. M. F. is set up in the armature in con- 
sequence. 

The ends of the magnetizing coils being suitably connected 
to the brushes, if these latter are in contact with the com- 
mutator, and a closed circuit through the field magnet wind- 
ings is formed, this small K. M. F. immediately sends a 
minute current through the exciting coils ; this immediately 
increases the strength of the magnetic field, and as a conse- 
quence an increased K. M. F. is induced in the armature. 
This results in a stronger current being sent through the 
exciting coils, and the increase of magnetism which follows 
results in an increased E). M. F. in the armature. 

Thus the process goes on, until eventually, for a given 
speed of rotation of the armature, the E. M. F. reaches a 
maximum value, beyond which it will not increase with- 
out a further increase in the speed of rotation ; the 
exciting current has then arrived at a constant value, 
and the magnetization of the machine will remain at 
a constant strength, and maintain the E. M. F. so long 
as the armature rotates at its normal speed. If the 
armature ceases to revolve, the field magnets will of course be 
deprived of their exciting current, and will therefore lose 
their magnetism ; the iron will, however, retain a sufficient 
amount of residual magnetism to again start the process when 
the machine is again started. 



152 NEW CATECHISM OF ELECTRICITY. 

FIELD MAGNETS. 

Whilst the construction of the armatures of different 
dynamos may be said to be very much the same, differing in 
small details only, and being confined to two types, viz., the 
ring and drum respectively, the construction of the field 
magnets varies greatly, almost every manufacturer having 
his own particular form and arrangement. This great variety 
in the form of the field magnets of different dynamos, is due 
in a large measure to consideration of economy involved in 
the manufacture by different makers, and also, to a less extent, 
to the different conditions under which a machine is required 
to work. For example, it is sometimes necessary for a 
machine to give a maximum of output with a minimum of 
weight, and under such circumstances the field magnet is 
constructed wholly of wrought-iron, and this necessarily 
entails an entirely different method of construction and 
arrangement than if cast-iron were employed. 

Again, as a rule, the direct coupling of the armature to the 
engine-shaft involves a different form of field magnet than 
would be the case if the armature were belt driven. 

Owing to difficulties of construction, and other considera- 
tions, field magnets are not in practice usually constructed 
out of a single-piece of iron, but are usually built up of a 
combination of parts, and composed either wholly of wrought 
or cast iron, or of a combination of both. 

The construction of a typical field magnet is illustrated in 
Fig. 75, from which it will be seen that it may be divided 
into five parts, viz.: — the two limbs of cores M M, upon which 



NKW CATECHISM OF ELECTRICITY. 



153 



Fig. 75. 



FIELD MAGNETS. 

the exciting coils C are wound ; the two 
end portions P P, called the '.' pole 
pieces," which are bored out so as to 
form the " armature chamber" within 
which the armature revolves ; and the 
yoke, Y, which serves to connect the two 
limbs together, and thus complete the 
magnetic circuit. The permeability of 
wrought-iron being very much greater 
than cast-iron, the portions M M of the 
field magnet, upon which the exciting coils are wound, are 
frequently constructed of this material ; these portion^ are 
also usually constructed of a circular section, and thus the 
amount of wire required for exciting the field magnet is 




TYPICAI, FIELD 
MAGNET. 



[Fig. 76. 



economized to the ut- 
most extent. The pole 
pieces P P and the 
yoke Y are in many 
cases of cast-iron, 
bolted on to the 
wrought-iron limbs. 

Although innumer- 
able forms of field 
magnets have been 
devised, they can all 
be arranged into two 
groups, viz., those in SALIENT POLE FIELD MAGNET. 

which the poles are " salient," and those in which the poles 




154 



NEW CATECHISM OF ELECTRICITY. 



FIELD MAGNETS. 

are ''consequent." A salient pole is the term applied to 
poles, which are produced at the ends of a bar of iron, in 
distinction to consequent poles, which are produced in a con- 
tinuous ring of iron. 

Fig. 77. 




THE OVERTYPE tflEl/D MAGNET. 



The salient pole form of field magnet, being least costly to 
construct, is most frequently met with in practice. Fig. 76 
shows its simplest form ; in this arrangement only one mag- 
netizing coil is required, this being wound upon the yoke 



NEW CATECHISM OF ELECTRICITY. 



155 



FIELD MAGNETS. 

which is usually of wrought iron, let into and bolted to the 
cast iron pole pieces N S. The paths and directions of the 
lines of force, with the magnetizing current flowing in the 



Fig. 78. 




THB UNTJERTYPB ItlKI/D MAGNET. 



direction shown, is indicated by the dotted arrow heads and 
lines. Another form of field magnet which is very exten- 
sively used, and in which two exciting coils are required, is 



i 5 6 



NEW CATECHISM OF ELECTRICITY. 



FIELD MAGNETS. 

shown in Fig. 77. In this type the limbs are usually of 
wrought-iron, of rectangular section, bolted to the bed place 
of the machine, which therefore forms the yoke of the mag- 
net. The magnetizing coils are wound upon bobbins, which 

Fig. 79. 




doublk field magnet. 



are slipped over the limbs, being held in place by the cast 
iron " horns" C C screwed on at the lower portion of the 
armature chamber. 

Consequent Pole Field Magnets.— The leading type 'of 
consequent pole field magnets are illustrated in Fig. 55. The 
paths and direction of the lines of force in the field and 
armature cores are indicated as before by the dotted arrow 
heads and lines. Fig. 55 may be looked upon as a double 



NEW CATECHISM OF ELECTRICITY. 157 

FIELD MAGNETS. 

magnet, the exciting coils being wound upon what may be 
regarded as the yokes of the magnets. The direction of the 
electric current flowing in the magnetizing coils are such that 
two similar poles are produced in each pole piece. 

The form of field magnet illustrated in Fig 77 is known 
as " the over type ; " when the armature is placed below the 
field coils and yoke, as represented in Fig. 78, the arrange- 
ment becomes "the under type." This latter form is very 
extensively used in large dynamos owing to the low centre of 
gravity of the revolving armature resulting in increased 
stability and freedom from vibration ; it is also invariably 
employed when the armature is to be coupled direct to the 
engine crank-shaft. In most cases the whole of the field 
magnet is composed of wrought- iron, the two limbs being 
formed of rectangular slabs bolted to the yoke. As a rule, 
this class of field magnet is supported upon a bedplate of cast 
iron, and therefore it is necessary to magnetically separate its 
pole pieces therefrom, otherwise they will be magnetically 
short circuited, or the lines of force will flow through the bed- 
plate in place of passing through the armature core. To 
effect this the pole pieces are supported at a suitable distance 
from the bedplate by "foot steps" S S or brackets of zinc, 
brass or other non-magnetic substance. 



Note.— It must always be borne in mind that in all dynamo-electric 
machines the electro-motive force generated is in proportion to the 
number of turns of wire in the rotating armature and to the speed of 
revolution, and the function, or use, of the magnetic field is to produce 
the proportionate needed lines of force. 



158 



NEW CATECHISM OF ELECTRICITY. 



FIELD MAGNETS. 

Multipolar Field Magnets. — These generally consist of 4, 
6, 8 or more poles, arranged in alternate order around the 
armature. They may be arranged in two classes according as 
the poles are salient or consequent poles. Fig. 80 represents 

Fig. 80. 




^C 




A \ 








p^v\ 






» 






1 






iffl * rnr 

• 


if, 






\ 




1 



MUI/riPOI,AR FlEl,D MAGNET. 



a very commonly used type of multipolar field magnet ; it 
consists of a ring of iron, having four pole pieces projecting 
inwardly, over which the exciting coils are slipped, the ring 
forming a common yoke for all the poles. As a rule, it is 



NEW CATECHISM OF ELECTRICITY. 159 

FIELD MAGNETS. 

made in two portions, bolted together horizontally, so that 
the upper portion may be lifted off for examination of the 
armature. 

Following the principles, or underlying laws, of the mag- 
netic circuit, the relative values of the very many typical 
forms of the field magnet may be judged by their approach 
to these general principles : 

i. Their permeability. 

2. Their compactness of form. 

3. Their firmness of joints. 

4. Their greatness of cross section. 

5. The softness of the iron of which they are composed. 



Fig. 81. 




I,IN3 WORK. 



NEW CATECHISM OF ELECTRICITY. 



Fig. 




sie^m^ns-hai.ske; machine;. 



NEW CATECHISM OF ELECTRICITY. 



COMMUTATORS. 



Fig. 83. 



These are collectors, or to use the old name, "com- 
muters," of the electric current. Their function or use is 
to collect the currents produced by the cutting of the lines of 
Torce so as cause them all to concur to 
a desired result. 

In general the commutator is 
formed of alternating sections of con- 
ducting and non-conducting material 
running longwise to the axis upon 
which it turns. Its place is in the 
shaft of the machine, so that it rotates 
therewith. Two brushes, or pieces of 
conducting material, press upon its 
surface. 




COMMUTATOR. 



The apparatus for collecting the currents of dynamo- 
machines may be divided into three types: 

First. Direct-current dynamos with closed-coil armatures, 
as used for incandescent lighting and other work requiring a 
constant or nearly constant potential, are furnished with a 
commutator consisting of a considerable number of parallel 



162 



NEW CATECHISM OF ELECTRICITY. 



THE COMMUTATOR. 

bars secured around an insulating hub, and presenting a 
cylindrical surface, against which press a pair (or in some 
cases more than one pair) of brushes or sets of brushes. 

Second. Direct-current dynamos of the open-coil type, 
as used for arc lighting, and giving a constant or nearly con- 
stant current, are provided with a commutator consisting 
of a comparatively small number of segments, each cover- 
ing a considerable angle, and separated by air-gaps from one 
another. 

Third. Alternators with revolving armatures need a pair 
of collecting rings of metal, each provided with one or more 



Fig. 84. 



brushes, or some analogous 
device to form a sliding con- 
nection with the circuit. 
Alternators with revolving 
field-magnets need a similar 
device to convey the exciting 
current to the moving coils. 

Fig. 84 represents a com- 
mutator consisting of Lr 
shaped bars bolted to a disk 
of slate and arranged so that 
the segments or parts are 
separated by an air space. 

Commutators are made in a great variety of forms. They 
are used on electric generators, on induction coils and else- 
where for changing the direction of the electric current* 




COMMUTATOR WITH AIR GAP. 



NEW CATECHISM OF ELECTRICITY. 163 

THE COMMUTATOR. 

" Points" Relating to the Commutator. — The number of 
bars of the commutator depends on the scheme of winding 
and on the number of sections in which the armature winding 
is grouped. 

Increasing the number of bars diminishes the tendency to 
spark, and lessens the fluctuations of the current. 

An even number of bars is preferable to an odd number ; 
and for ring- wound armatures the cores of which are usually 
carried on three-armed spiders, it is preferable that the num- 
ber of bars should be a multiple of three. There are, how- 
ever, two practical reasons against making the number of bars 
very great. Increasing the number increases the cost. Again, 
in large machines having but one turn of the armature wind- 
ing from each bar of tha armature to the next, the number 
cannot be greatly increased without exceeding the voltage 
desired. 

On the other hand, it is found for small dynamos, that if 
the number of bars is increased, each bar becomes so thin, 
that a brush of the proper thickness to collect the current 
would lap over, or bridge, more than two commutator bars at 
once. 

The bars should be of a length proportionate to the num- 
ber of amperes that is to be taken off at them. Modern 
practice varies somewhat, but it may fairly be represented by 
some such figure as (1.2) 1 i-5th inches for 100 amperes. 

The mode of attachment of the bars should be such as to 
make the greatest amount of length available. 



164 NEW CATECHISM OF ELECTRICITY. 

THE COMMUTATOR. 

They should also be of considerable thickness to allow 
them to be turned off occasionally to preserve their round- 
ness. 

As for the material most makers use hard drawn copper, 
made in long lengths of the proper section and cut off to .the 
length required. It is needful to have a good insulati n be- 
tween each bar and its neighbors, and a specially good insula- 
tion between the bars and the sleeve or hub around which 
they are mounted, and also between the bars and the clamp- 
ing devices that hold them ; for the difference of potential is 
small between neighboring bars, and much larger between 
the bars and other metal-work. The insulating material must 
not absorb oil or moisture ; hence asbestos and plaster are 
inadmissible. Vulcanized fibre and paper are not by them- 
selves adequate, though mechanically strong. Mica is the 
only satisfactory material. 

Although the application of the commutator to the coil has 
the effect of causing the current to flow always in the same 
direction in the external circuit, it has no effect whatever upon 
the value of the K. M. F., or the strength of the current, dur- 
ing a complete revolution of the coil. This still remains as 
before. 

The commutator bars are the separated segments or parts 
upon which the brashes rest. 

Alternators have no commutator, but they usually need a 
pair of sliding contacts to convey the currents to and from 
the rotating part. The usual device is a pair of contact rings 



NEW CATECHISM OF ELECTRICITY. 



I65 



THE COMMUTATOR. 

of copper or gun-metal mounted on insulating hubs on the 
shaft, with one or more brushes to press on each contact-ring. 
In those alternators in which the revolving part is the arma- 
ture, great care must betaken to insulate well the two rings 
from each other, and from the shaft. 

Commutators with air-gaps between the bars have been 
used but the difficulty is to keep the gaps from being filled 
by the metallic dust produced by the wearing of the brushes. 



Fig. 85. 




INCANDESCENT UMP SHADE. 



i66 



NEW CATECHISM OF ELECTRICITY. 




EAU CLAIRE, WIS., MACHINE. 



NEW CATECHISM OF ELECTRICITY. 



167 



THE BRUSHES. 



The brushes bear upon the commutator, and make sliding 
contact with the armature and working circuits. It is needful 
that they should have a certain amount of flexibility, in order 
that they may accommodate themselves to any little in- 
equality which may occur upon the surface of the commutator, 

Fig. 87. 




and also to avoid cutting or scoring the latter ; with these 
objects, they are usually made of copper or brass gauze, wire, 
or flexible strip. 

Gauze Brushes. — This type of brush is now very exten- 
sively used, owing to its great flexibility and soft and yieldicg 
nature, resulting in decreased wear of the commutator. It is 



l68 NEW CATECHISM OF ELECTRICITY. 

THE BRUSHES. 

made up of a sheet of copper gauze, folded round several 
limes, with the wires running in an oblique direction, so as to 
form a solid flat strip of from X mcn to % mcn m thickness, 
as shown at A, Fig. 87, the thickness increasing with the 
volume of the current to be collected. The object of folding 
the gauze up with the wires running in an oblique direction 
is to prevent the ends of the brushes fraying or threading out, 
which would be the case if the gauze was folded up in any 
other manner. 

Wire Brushes. — This brush (B. Fig. 87) which was much 
used previous to the invention of the gauze brush, is made up 
of a bundle of brass or copper wires, laid side by side and 
soldered together at one end, being harder than the gauze 
brush, it is more liable to cut or score the commutator > and it 
is also more troublesome to trim. 

Strip Brush. — This is probably the simplest form of brush, 
but is not very extensively used owing to its lack of flexibility. 
It consists of a number of strips of copper or brass, laid one 
upon the other and soldered at one end, as in C, Fig. 87. 

Carbon Brushes. — When metallic brushes are used upon 
the commutators of high tension machines, they frequently 
give rise to excessive sparking, and also heating of the arma- 
ture, the metallic dust given off appearing to lodge between 
the segments of the commutator, thus partially short circuit- 
ing the armature. To obviate this, carbon brushes are fre- 
quently used on such dynamos, this substance being found 
very effectual in the prevention of sparking. The brushes 



NEW CATFXHISM OF ELECTRICITY. 1 69 

THE BRUSHES. 

are usually in the form of oblong blocks placed " butt " end 
on the commutator, and fed forward as they wear away by 
means of a spring holder. 

Wheel Brushes have been employed among the many de- 
vices for collecting the current. These consist of small 
wheels, or disks, bearing against and rotating on the surface 
of the commutator. 

Lead of the Brushes is the dispacement or lead in advance 
of, or beyond the position at right angles to the line connect- 
ing the poles of the field magnet. In a motor the brushes 
are set back of the right angle or are given a negative lead. 

The necessity for the lead arises from the counter magnet- 
ism or the magnetic reaction of the armature. In magnetism 
the tendency of hard iron, or steel especially, is the cause of 
the "lag" or magnetic retardation. It is to accommodate 
this variation that brush holders are provided with devices for 
moving them backward and forward. 



Note.— Flexible Carbon Brushes— Carbon commutator brushes, as 
commonly used, consist of one or two blocks of carbon, pressed against 
the commutator by a spring to maintain the contact. In the case of street 
railway motors, subject to violent oscillations, the carbons are often 
jolted away from the commutator, thus causing sparks and burning of 
the commutator. In order to dispense altogether with springs and at the 
same time to maintain the pressure constant, Professor Geo. Forbes of 
London, has devised a brush of flexible carbon, carbonized cloth, com- 
pressed into a metal case open at the side, facing the commutator, the 
case serving both as a holder for the flexible carbon, and also as a ter- 
minal for the circuit ; owing to its flexibility, it maintains contact with 
the commutator at an infinite number of points. By this means it is as- 
serted a much better contact is maintained, which is not broken, or even 
varied, by the jolting on a railroad car. 



i7o 



NEW CATECHISM OF ELECTRICITY. 



THE BRUSHES. 

In all well-designed dynamos not less than two brushes are 
used on each side of the commutator ; this allows of either 
brush being removed, and examined and trimmed, while the 
machine is running. It also allows of the brushes being ad- 

Fig. 88. 





VARIOUS KINDS OF BRUSHES. 



justed upon the commutator independently of each other, any 
uneven wear of the commutator being thus prevented, and 
better contact made. 

Brush Holders. — In order to secure sparkless collection of 
the current, and to prevent undue wear of the commutator, it 
is needful that the pressure of the brushes upon the latter 



NEW CATECHISM OF ELECTRICITY. 171 



THE BRUSHES. 

should be capable of being adjusted to meet requirements ; it 
is also needful that they should be capable of being fed for- 
ward as required and that they be furnisued with a movement 
to permit of the brushes being raised from contact with the 
commutator when necessary. 

Brush Rockers, — As previously mentioned, when a dynamo 
is working, the neutral points, or the points upon the com- 
mutator where sparkless collection of the current can be 
made, vary in position as the load upon the dynamos varies, 
moving round in the direction of rotation as the load increases, 
and vice versa. It is necessary, therefore, in order to avoid 
sparking, to shift the brushes bodily upon the commutator 
from time to time, without in any way altering the adjustments 
of the brush holder springs or breaking the working circuit. 
To enable this to be effected the brushes with their holders 
are, in ordinary bi-polar dynamos, usually fixed upon a 
" rocker" or "yoke." 

Points relating to Brushes— The brushes must be held 
firmly, and joined with a good metallic contact to their 
circuit. 

Brush-holders must permit brushes to be withdrawn or fed 
forward as required. 

Brushes must be held to make contact at proper angle to 
the surface of the commutator. 

Brushes must bear with proper pressure upon the com- 
mutator ; if too light, they will jump and spark ; if too heavy, 
they will cut the commutator into ruts, 



172 NEW CATECHISM OF ELECTRICITY. 



THE BRUSHES. 

Brush- holders must permit brushes to be raised from con- 
tact. 

They must also permit, by a proper mechanical catch, of 
the brushes being held raised out of contact. 

Insulated handles should be provided for all dynamos work- 
ing above ioo volts, so that the brushes may be raised and 
adjusted without risk of shocks. 

The insulation of the brush, or of brush and brush-holder 
together, must be very thorough. 

Each maker has his own particular arrangement for giving 
these essential motions to the brushes and they are best illus- 
trated in the various ' ' cuts ' ' of dynamos and motors to be 
found on other pages. 



NEW CATECHISM OF ELECTRICITY. 1 73 



DYNAMO FOUNDATIONS, ETC. 



"Points" relating to the dynamo. — The place chosen for 
the dynamo should be dry, free from dust, and preferably 
where a cool current of air can be had. It should allow a 
sufficient room for a belt of proper length, unless the dynamo 
is direct-driven. 

It is most important to secure good foundations for every 
dynamo ; and if the dynamo is direct-driven, but is not on the 
same bed-plate as the engine, a foundation large enough for 
both together should be laid down. Stone or concrete may 
be used, or brick built with cement, having a large thick stone 
bedded at the top. For small dynamos the holding-down 
bolts may be set with lead or sulphur in holes in the stone 
top ; but for large dynamos the bolts should be long enough 
to pass right down to the bottom, where they should be 
secured into iron plates built in. If long holes are left in the 
foundations for the holding-down bolts they should be filled 
in with thin cement after the latter have been put in place. 

All belt- driven dynamos ought to be provided with tight- 
ening gear to take up the slack. If the dynamo is not pro- 
vided with sliding rails under its bed-plate and tightening 
screws, the less desirable method of employing a tenting 
pulley, may be used. In any case the bed for dynamo must 
be quite level, and the shaft set properly parallel with the 
driving pulley. 



174 



NEW CATECHISM OF ELECTRICITY. 



Fig. 89 




WINDSOR (CONN.) MACHINE. 



1 



NEW CATECHISM OF ELECTRICITY. 1 75 



CARE AND MANAGEMENT OF THE DYNAMO. 



When the machine has been securely fixed, and previous 
to the first starting, the whole of the machine should be care- 
fully examined to see that all parts are in good order, and 
have not been damaged. The field magnet circuit should 
first be inspected to see that none of the wires or connections 
have been broken or are loose, and that the coils are correctly 
coupled up. The caps of the bearings should next be taken 
off, and these and the journals carefully cleaned from all grit 
and dirt. They should then be oiled, and the caps replaced 
and screwed up with the hand only. The gaps between the 
outer surface of the armature and the polar faces should be 
examined in order to ascertain whether any foreign body, 
such as a small screw or nail has lodged therein. If such is 
the case, it should be carefully removed with a bit of wire. 

The guard plates protecting the armature windings should 
also be removed, and the windings carefully inspected by 
slowly rotating the armature, to see that they are not dam- 
aged, and that the insulation is perfect. The armature should 
then be finally rotated by hand to see that it revolves freely, 
and that the bearings are securely fixed. 



176 NEW CATECHISM OF ELECTRICITY. 

CARE AND MANAGEMENT OF THE DYNAMO. 

The commutator and brushes should next receive atten- 
tion — the commutator, to see that it is not damaged in any 
way through one or more of the segments being knocked in, 
or the lugs being forced into contract with one another ; and 
the brush-holders and brushes, to see that the latter are clean 
and make good contact with the brush-holders or flexible 
leads, and the former to see that they work freely on the 
spindle, and that the hold-off catches work properly. 

In the subsequent working of the dynamo it will of course 
not be necessary to follow the whole of these proceedings every 
time the machine is started, as it is extremely unlikely that 
the machine will be damaged from external causes whilst 
working without the attendant being aware of the fact. 
Having ascertained that the machine is not injured in any 
way, and that the armature revolves freely, the adjustment of 
the brushes should next be proceeded with. 

Attention to Brushes. — The adjustment of the brushes 
upon the commutator requires careful attention if sparking is 
to be avoided. The points upon the commutator at which the 
tips of the brushes, carried by opposite arms of the rocker, 
bear upon the commutator, should be, in bi-polar dynamos, 
at opposite extremities of a diameter. In multipolar dynam: s 
the positions vary with the number of poles and the nature 
of the armature winding. In order to facilitate the correct 
setting of the brushes upon the commutator, setting marks 
are usually cut in the collar of the commutator next to the 
bearing. 



NEW CATECHISM OF ELECTRICITY. 177 

CARE AND MANAGEMENT OF THE DYNAMO. 

In bi-polar dynamos, these setting marks divide the cir- 
cumference of the commutator into equal parts. In adjusting 
the brushes, the tips of all the brushes carried by one arm of 
the rocker are set in correct line with the commutator seg- 
ment marked out by one setting mark, and the tips of the 
brushes carried by the other arm or arms are set in correct 
line with the segments marked out by the other mark or 
marks. 

If one or more brushes in a set are out of line with their 
setting mark, it will be necessary to adjust the brushes up to 
this mark by pushing them out or drawing them back, as 
may be required, afterwards clamping them in position. 
When adjusting the brushes the armature should always be 
rotated, so that the setting marks are horizontal. The rocker 
can then be rotated into position, and the tips of both sets of 
brushes conveniently adjusted to their marks. In those brush- 
holders provided with an index or pointer for adjusting the 
brushes the setting marks upon the commutator are absent, 
length of the pointer being so proportioned that when the 
tips of the brushes are in line with the extreme tips of the 
pointers, the brushes bear upon the correct positions on the 
commutator. 

Having adjusted the brushes to their correct positions upon 
the commutator, their tips or rubbing ends should next be 
examined, whilst in position, to see that they bed accurately 
on the surface of the commutator. In many instances it will 
be found that this is not the case, the brushes sometimes 



J 7 8 NEW CATECHISM OF ELECTRICITY. 

CARE AND MANAGEMENT OF THE DYNAMO. 

bearing upon the point or toe, and sometimes upon the heel, 
so that they do not make contact with the commutator 
throughout their entire thickness and width. The angle of 
the rubbing ends will therefore need to be altered by filing to 
make them lie flat. 

When the brushes do not bed properly upon the commu- 
tator, and filing has to be resorted to in order to alter the 
angle of the brush tips or ends, it will be found necessary to 
fix the brush in a holder or filing clamp, in order that the 
correct angle may be conveniently obtained. This, as a rule, is 
supplied with the machine, and consists of two pieces of 
metal, both shaped at one end to the correct angle (usually 
45 ), to which the brushes must be filed. One of the pieces of 
metal (the back part) has a groove sufficiently large to accom- 
modate the brush, which is clamped in position by the other 
piece of metal and a pinching screw. 

If the clamp is not supplied, a convenient substitute can 
be made out of two pieces of wood about the same width as 
the brush. One end of each piece of wood is sawn to the 
correct angle, and the brush is placed between the two. In 
filing, the brush is fixed in the clamp, with the toe or tip pro- 
jecting slightly over the edge of the clamp, and the latter 
being fixed in a vice, the brush is filed by single strokes of a 
smooth file made outwards, the file being raised from contact 
with the brush when making the back stroke. 

Having ascertained that the brushes are correctly placed 
and bedded upon the commutator it remains to adjust their 



NEW CATECHISM OF ELECTRICITY. I7g 

CARE AND MANAGEMENT OF THE DYNAMO. 

pressure upon the latter. This is effected by regulating 
the tension of the springs provided for the purpose upon the 
brush-holders. The tension of the springs should be just 
sufficient to cause the brushes to make a light yet reliable 
contact with the commutator. The contact must not be too 
light, otherwise the brushes will vibrate, and thus cause 
sparking ; nor must it be too heavy, or they will press too 
hard upon the commutator, grinding and scoring and wearing 
away the latter and themselves to an undesirable extent, and, 
moreover, giving rise to great heating and sparking. 

The correct pressure is attained when the. brushes collect 
the full strength of current without sparking, while their 
pressure upon the commutator is just sufficient to overcome 
any ordinary vibration due to the rotation of the commutator. 

Adjusting Lubricators. — As a rule, sight feed lubricators 
are used in all but the smallest machines. Previous to start- 
ing, these vshould be examined to see that they feed the 
lubricant properly, and that the oil passages are not clogged. 
They should then be adjusted to feed an ample supply of oil 
on to the armature spindle. The amount required will of 
course depend upon the load and the nature of the oil used, 
but from 3 to 12 drops per minute of any ordinary heavy 
hydro carbon oil is generally sufficient for a load varving 
from 6 to 30 horse-power. 

Starting Dynamos. — Having attended to the above pre- 
liminaries, and having cleared all keys, spanners, bolts, &c, 
out of the immediate neighborhood of the machine, and 



i8o 



NEW CATECHISM OF ELECTRICITY. 



Fig. 90. 




DAYTON (OHIO) MACHINE. 



NEW CATECHISM OF ELECTRICITY, l8l 

CARE AND MANAGEMENT OF THE DYNAMO. 

having raised the brushes from contact with the commutator 
by means of the hold-off catches, the dynamo may be started 
and allowed to run light. 

Whilst thus running, the bearings should be tested from 
time to time to ascertain if they heat unduly, and an oppor- 
tunity is also afforded, while the dynamo is thus running, foi 
cleaning the commutator, if this is dirty, with finest emery 
cloth, afterwards wiping clean with a linen rag. The con- 
nections of the machine and external circuits should be veri- 
fied, and all terminals, &c, cleaned and examined. If found 
correct, the brushes should be let down on to the commutator, 
and their tips adjusted by rotating the rocker into the neutral 
points. 

The tips of the brushes carried by one arm of the rocker 
will, in bi-polar dynamos with vertical field magnets, bear 
exactly upon the top or highest point of the commutator, 
while the tips of those carried by the other arm will bear 
exactly upon the bottom or lowest point of the commutator. 
In other types of machines, the positions for the brushes will 
vary according to the class or form of the field magnet and 
the system of armature winding. If the machine is com- 
pound or shunt wound, all switches controlling the external 
circuits should be opened, as the machine excites best when 
this is the case ; and when the machine is provided with a 
rheostat or hand regulator and resistance coils, these latter 
should all be cut out of circuit, or short circuited, until the 
machine excites, when they can be gradually cut in as the 
voltage rises. 



1 82 NEW CATECHISM OF ELECTRICITY. 

CARE AND MANAGEMENT OF THE DYNAMO. 

When the machine is giving the correct voltage, as indi- 
cated by the voltmeter or pilot lamp, the machine may he 
switched into connection with the external or working cir- 
cuits. When the machine is series wound, it is absolutely 
necessary to have the external circuit closed, otherwise a 
closed circuit will not be formed through the field magnet 
windings, and the machine will not excite. 

Attention to Dynamo after it is started. — When the 
machine is started and at work, it will need a certain amount 
of attention to keep it running in a satisfactory and efficient 
manner. The first point to which attention should be paid is 
the adjustment of the "lead" of the brushes. If this is 
neglected, the machine will probably spark badly, and the 
commutator and brushes will constantly require filing and 
trimming. The "lead" is the term applied to the slight 
forward movement which it is found necessary to give to the 
brushes of most dynamos in order to avoid sparking with an 
increase of load 

This lead in all good dynamos is very small, and varies 
with the load and class of machine. The best lead to give to 
the brushes can in all cases be found by rotating the rocker 
and brushes in either direction to the right or left of the neu- 
tral points, until sparking commences increasing with the 
movement. The position midway between these two points 
is the correct position for the brushes, for at this position the 
least sparking occurs, and it is at this position that the 
brushes should be fixed by clamping the rocker. 



NEW CATECHISM OF ELECTRICITY. 1 83 

CARE AND MANAGEMENT OF THE DYNAMO. 

In series dynamos giving a constant current, such as for 
arc lamps in series, the brushes require practically no lead. 
In shunt and compound dynamos the lead varies with the 
load, and therefore the brushes must be rotated in the direc- 
tion of rotation of the armature with an increase of load, and 
in the opposite direction with a decrease of load. 

In cases where the dynamos are subjected to a rapidly 
varying or fluctuating load, it is of course not possible to con- 
stantly shift the brushes as the load varies, therefore the 
brushes should be fixed in the positions where the least 
sparking occurs at the moment of adjustment. If at any 
time very violent sparking occurs, which cannot be reduced 
or suppressed by varying the position of the brushes by rotat- 
ing the rocker, the machine should be shut down at once, 
otherwise the commutator and brushes are liable to be de-. 
stroyed, or the armature burnt up. This especially refers tc 
high tension machines. 

As soon as any abnormal sparking is seen at the com 
mutators of such machines, their speed should be at once, 
reduced, and the commutator cleaned up, and the brushes 
readjusted. Another very important point to be looked to is 
the lubrication of the machine. The lubricators should be 
inspected from time to time, to see that they feed the lubricant 
properly, and that none of the waste oil passages are clogged. 
The oil should on no account be allowed to get on to the 
commutator or brushes, or into the windings of the armature, 
as it is liable to cause sparking at the brushes, and to destroy 
the insulation of the armature. 



184 NEW CATECHISM OF ELECTRICITY. 



CARE AND MANAGEMENT OF THE DYNAMO. 

Ill filling the lubricators, oil cans made of some non- 
magnetic material such as copper, brass or zinc, should always 
be used. If iron cans are used, they are liable to be attracted 
by the field magnets, and thus possibly catch in the armature, 
and destroy the insulation of the latter. The bearings, and 
also the field magnet coils, should be tested at intervals, to 
see that they do not become unduly heated. When testing 
the temperature of low tension machines, the hand may be 
used as a guide forjudging when the machine is running at a 
safe temperature. 

If the heat of any portion can be easily borne by the 
naked hand, it may be taken that the temperatnre of the 
machine is within safe limits. In the case of high tension 
machines, however, the naked hand cannot be brought with 
safety into contact with any portion of the machine, and 
therefore the only way to ascertain if the windings or other 
electrical parts are at a safe temperature is to apply a ther- 
mometer. 

It may be taken as a safe rule that no part of a working 
dynamo should have a temperature of more than 8o° Fahr. 
above that of the surrounding air. Hence, if the temperature 
of the engine-room is noted before applying the thermometer 
to the machine, it can at once be seen if the latter is working 
at a safe temperature. In taking the temperature, the bulb 
of the thermometer should be wrapped in a woolen rag. The 
screws and nuts securing the different connections and cables 
should be examined occasionally, as they frequently work 
loose through the vibration. 



NEW CATECHHM OF ELECTRICITY. 185 

CARE AND MANAGEMENT OF THE DYNAMO. 

' Attention to Brushes and Commutator. — The brushes and 
commutator are the most troublesome parts of a dynamo and 
requite most attention. To keep them in a satisfactory work- 
ing condition, the main thing to be guarded against is the 
production of sparking at the brushes. If care be taken in 
the first instance to properly adjust the brushes* to their 
setting marks, and their pressure upon the commutator, and 
afterwards to attend to the lead as the load varies, so that 
little or no sparking occurs, and to keep the brushes and 
commutator free from dirt, grit, &c, and excessive oil, the 
surface of the commutator will assume a dark burnished 
appearance, and all wear will practically cease. 

Under these circumstances the commutator will run cool, 
and free from sparking, and will give very little trouble. In 
order to maintain these conditions it will only be necessary to 
see that the brushes are properly trimmed and fed forward to 
their setting marks, as described above, as they wear away, 
and that the commutator is occasionally polished with the 
finest emery cloth. If, on the other hand, the pressure of the 
brushes upon the commutator is too great, or their adjustment 
is faulty, or the commutator is allowed to get into a dirty con- 
dition, sparking will inevitably result, and, if not at once 
attended to and remedied, the brushes will quickly wear 
away, and the surface of the commutator will be destroyed. 

If this condition of things is allowed to continue, matters 
will rapidly get worse. In the earlier stages, the surface of 
the commutator will become roughened or scored, resulting 
in jumping of the brushes, and increased sparking ; in the 



1 86 NEW CATECHTSM OF ELECTRICITY. 

CARE AND MANAGEMENT OF THE DYNAMO. 

later stages, the commutator will become untrue and worn 
into ruts, and owing to the violent sparking which takes place 
through this circumstance, the machine will quickly be ren- 
dered useless for practical purposes. 

When once started, the only way to remedy this condition 
of things is to repolish the commutator and readjust the 
brushes, as directed above. If the commutator is merely 
scored, a smoth file applied while the armature is revolving, 
with a final polishing with coarse and fine emery cloth, will 
generally put things into a satisfactory condition. If, how- 
ever, the commutator is worn into deep ruts, or is untrue, 
nothing short of putting the armature in the lathe and re- 
turning the commutator will make a good job of it. 

When carbon brushes are used, a little extra special at- 
tention should be given in keeping the commutator per- 
fectly clean, otherwise it is liable to heat up through short 
circuits, caused by carbon dust lodging between the segments. 
When carbon brushes are working properly, the fact is indi- 
cated by a uniform greyish tinge being imparted to the com- 
mutator, with a total absence of heating or sparking of any 
description. 

If the surface of the commutator assumes a mottled or 
streaky appearance, accompanied by small sparks flashing 
from segment to segment, it is advisable to slow down the 
machine and clean up the commutator at once. When either 
metal or carbon brushes are used, the surface of the com- 
mutator is bound in course of time to undergo a certain 



NEW CATECHISM OF ELECTRICITY. 187 

CARE AND MANAGEMENT OF THE DYNAMO. 

amount of wear, even when the greatest care is taken to 
reduce sparking. 

In order to prevent this wear giving rise to ruts or ridges 
upon the surfaces of the commutator, it is advisable to shift 
the brush-holders and brushes upon the rocker arm, if this is 
possible, from time to time. The unequal wear of the com- 
mutator may also be prevented by so arranging the brushes 
carried by one arm of the rocker that they cover the gaps 
between the brushes carried by the other arm of the rocker. 
The armature spindle or shaft is also given a little end play in 
order to prevent this grooving. 

Lubricant on Commutator. — In most cases it will be found 
that a little lubricant is needed on the commutator in order 
to prevent cutting of the latter by the brushes, and this is 
especially the case when hard strip brushes are used. The 
quantity of oil so used should be very small — a few drops 
smeared upon a piece of clean rag, and applied to the commu- 
tator while running, being quite sufficient. * It is advisable to 
use mineral oil, such as vaseline, or any other hydro-carbon. 
Animal or vegetable oils should be avoided, as they have a 
tendency to carbonize, and thus cause short-circuiting of the 
commutator, with attendant sparking. 

Trimming Brushes. — At certain intervals, according to 
the care taken to reduce sparking, and the length of time the 
machine runs, the brushes will fray out or wear unevenly, 
and will therefore need trimming. They should then be 
removed from the brush-holders, and their contact ends or 



iS8 



NEW CATECHISM OF ELECTRICITY. 



Fig. 91. 




AMERICAN GIANT DYNAMO. 



NEW CATECHISM OF ELECTRICITY. 1 89 

CARE AND MANAGEMENT OF THE DYNAMO. 

faces examined. If not truly square, they should be filed or 
clipped with a pair of shears, the course of treatment differing 
with the type of brush. 

If metal strip brushes, the feathered-out ends should' be 
clipped square with a pair of shears, the ends thoroughly 
cleaned from any dirt or carbonized oil, and replaced in their 
holders. Gauze and wire brushes require a little more atten- 
tion. When their position on the commutator has *been well 
adjusted and looked after, so that little or no sparking has 
taken place, it will generally be only found necessary to wipe 
them clean, and clip off the fringed edges and corners with 
the shears, or a pair of strong scissors. If, however, the ma- 
chine has been sparking, the faces will be worn or burnt 
away, and probably fused. If such is the case, they will need 
to be put in the filing clamp, and filed up square and true, as 
directed above. 

If the contact faces of the brushes are very dirty and cov- 
ered with a coating of carbonized oil, &c, it will be necessary 
to clean them with benzoline or soda solution before replacing. 
The handiest way of trimming carbon brushes, or of bedding 
a complete new set of metal brushes, is to bind a piece of 
emery cloth or sand paper, face outwards, around the com- 
mutator after the current has been shut off, and then mount 
the carbon or metal brushes in the holders, adjusting the ten- 
sion of the springs so that the brushes bear with a moderately 
strong pressure upon the emery cloth or sand paper. 

Then let the machine run slowly until the ends of the 
brushes are ground to the proper form. Care should be taken, 



I9O NEW CATECHISM OF ELECTRICITY. 

CARE AND MANAGEMENT OF THE DYNAMO. 

however, that the carbon or metal dust given off does not get 
into the commutator connections or armature windings, or 
short circuiting will result. If it becomes necessary, through 
sparking or other causes, to trim the brushes while the ma- 
chine is working, one brush at a time should be removed 
from the holders. 

The brush to be removed should first be raised carefully 
from the commutator ; then, if excessive sparking or heating 
occurs, the brush should be let down again, and the tension of 
the springs of the brushes temporarily increased until the 
brushes are trimmed. This of course only applies to machines 
provided with at least two brushes to each set. If only one 
brush is provided, the machine must be stopped before the 
brushes can be trimmed. 



SHUTTING DOWN DYNAMO. 



When shutting down a machine, the load should first be 
gradually reduced, if possible, by easing down the engine ; 
then, when the machine is supplying little or no current, the 
main switch should be opened. This reduces the sparking at 
the switch contacts, and prevents the engine racing. 



NEW CATECHISM OF ELECTRICITY. igi 

CARE AND MANAGEMENT OF THE DYNAMO. 

When the voltmeter almost indicates zero, the brushes 
should be raised from contact with the commutator. This 
prevents the brushes being damaged in the event of the engine 
making a backward motion, which it often does, particu- 
larly when it is a gas-engine. On no account, however, 
should the brushes be raised from the commutator while the 
machine is generating any considerable voltage ; for not only 
is the insulation of the machine liable to be damaged by this, 
proceeding, but in the case of large shunt dynamos an ex- 
ceedingly violent shock is liable to be administered to the 
person lifting the brushes. 

When the dynamo is at rest, or only revolving slowly, and 
the brushes are raised from the commutator, the latter should 
be cleaned up, if this is necessary. In dusty places, such as 
flour mills, sugar works, cement works, &c, it will probably 
be necessary to clean off the commutator with benzoline, and 
finally with finest emery cloth, at the end of every run. In 
places free from dust, it will only be necessary to wipe the 
revolving surface perfectly clean, or until it will not soil a 
white rag, and occasionally to apply a little fine emery cloth 
before stopping. 

When the machine is stopped it should be thoroughly 
cleaned up. The armature should be dusted with a pretty 
stiff brush from any adherent copper dust, dirt, &c, and the 
other portions of the machine should be thoroughly cleaned 
with linen rags. Waste should not be used, as it is liable to 
leave threads, fluff, &c, on the projecting parts, terminals 



192 wew catechism of electricity. 



CARE AND MANAGEMENT OF THE DYNAMO. 

and other parts of the machine, and on the windings of the 
armature, which is very difficult to remove. 

The brushes-should be examined, and if necessary trimmed 
and adjusted, and all terminals, screws, bolts, &c, carefully 
cleaned and screwed up ready for the next run. The brush- 
holders should receive special attention, as when dirty they 
are liable to stick and cause sparking. All dirt and oil should 
be removed from the springs and contacts, and pivots and 
other working parts, 

It is advisable at stated intervals to entirely remove the 
brush-holders from the rocker arms, and give them a thorough 
clean up, by taking them to pieces, and cleaning each part 
separately with emery cloth and benzoline or soda solution. 

Another point to which particular attention should be 
given is the cleaning of the brush rocker. This being com- 
posed wholly of metal, and the two sets of positive and nega- 
tive brushes being only separated from it by a few thin 
insulating washers, it follows that if any copper dust given off 
by the brushes is deposited in the neighborhood of these 
washers, there is considerable liability for a dead short circuit 
of the machine to occur, by the dust bridging across the 
insulation. 

These particular parts should therefore be kept scrupulously 
clean and free from any conducting matter. It is a good 
plan, when the machine has been thoroughly cleaned up and 
all connections made secure, to occasionally test the insulation 
of the different parts. If a record is kept of these tests, any 



I 



NEW CATECHISM OF ELECTRICITY. 



193 



CARE AND MANAGEMENT OF THE DYNAMO. 

deterioration of the insulation of the machine can at once be 
detected, localized and remedied before it has got far enough 
to cause a breakdown. 

As a means of protecting the machine from any moisture, 
dirt, &c, while standing idle, it is advisable to cover it, up 
with a suitable waterproof cover. 



PRACTICAL RULE FOR COUPLING UP FIELD 
MAGNET COILS. 



Iu coupling up the coils of either salient or consequent pole 
field magnet coils, assume each of the pole pieces to have a 
certain polarity ( in bi-polar dynamos two poles only, a north 
and south pole respectively, are required ; in multipolar dy- 
namos the poles must be arranged in alternate order around 
the armature, the number of N and S poles being equal), then 
apply the rule given on page 81 to each of the coils, and ascer- 
tain the direction in which the magnetizing current must flow 
in each in order to produce the assumed polarity in each of 
the pole pieces. Having marked these directions on the coils, 
the coils can be coupled up in either series or parallel accord- 
ing to requirements, so that the current flows in the necessary 
direction in each. 



194 



NEW CATECHISM OF ELECTRICITY. 



CARE AND MANAGEMENT OF THE DYNAMO. 

Connecting Up Dynamos. — The manner in which the con- 
nections of the field magnet coils, and brnshes, and terminals,, 
are connected to one another, depends entirely upon the class 
of dynamo. The field magnet shunt coils of shunt and com- 
pound wound dynamos, are invariably arranged in series with 
one another, and then connected as a shunt to the brushes or 
terminals of the machine, as represented in Figs. 61 and 62. 
The series coils of series and compound wound machines, are 
arranged either in series or in parallel with one another, ac- 
cording to circumstances, and the amount of current given 
by the machine, and then connected in series to the armature 
and external circuits upon the principle shown in Figs . 60 
and 61. 



Fig. 92. 




WATER METER FOR POWER STATIONS,. 



NEW CATECHISM OF ELECTRICITY. I95 



SYMBOLS, ABBREVIATIONS AND 
DEFINITIONS. 



Quks. What is the meaning of the terms "bug" and 
"bug trap" ? 

Ans. The term bug is used to a limited extent to designate 
any fault or trouble in the connections or working of electric 
apparatus. The "bug trap" is the arrangement or connec- 
tion for overcoming the * ' bug. ' ' 

These terms are said to have originated in quadruplex 
telegraphy and been transferred to all electric apparatus. 

QuKvS. What is the meaning of l ' synchronous ' ' f 

Ans. It means the occurrence of two events at the same 
time ; caused to act together or occur simultaneously. 

Quks. Where and how is the word used ? 

Ans. It is used in telegraphy — in the ' * step-by-step " 
system ; with alternating current dynamos, where two are 
used together, it is necessary that they are " synchronized " — 
i. e., act together, since otherwise the machine may suffer. 

Motors of the "synchronous type," are so called because 
they run at the same speed or in a certain proportion to the 
speed of the generator. 



Note. — See page 114. 



196 



NEW CATECHISM OF ELECTRICITY. 



Fig. 93. 




NEW CATECHISM OF ELECTRICITY. I97 



REGULATING DYNAMOS. 



Means of governing the performance of dynamos are 
needed, not only for keeping the pressure at some constant 
number of volts or for keeping current at some constant 
number of amperes, but also for such purposes as to enable 
the voltage of any one dynamo to be raised in order 
that it may feed into some distant point of a distributing 
network. 

The output of a dynamo may be regulated or varied by 
any of the following methods, or by a combination of the 
same: (i) Variation of speed of armature. (2) Variation 
of strength of magnetic field. (3) Variation of position of 
brushes on commutator. (4) Variation of resistance in dy- 
namo circuit. The application of these methods of regula- 
tion to the various classes of dynamos is considered in the 
succeeding paragraphs. 

Regulating Separately Excited Dynamos. — The voltage 
and output of this class ot machine is most commonly gov- 
erned by varying the strength of the magnetizing current 
flowing through its field magnet coils. When the magnetiz- 
ing current is furnished by a battery or accumulator, this is 



I98 NEW CATECHISM OF ELECTRICITY. 



REGULATING DYNAMOS. 

effected either by means of a hand regulator or rheostat 
inserted in the exciting circuit (as represented in Fig. 94), or 
by varying the number of cells in circuit, this latter being 
the most economical plan. In most cases, however, a smaller 
dynamo is used for the purpose. In this case the strength of 
the magnetizing current flowing in the coils of the main dy- 
namo may be regulated by either of two methods : (a) by 
means of a hand regulator inserted in the field circuit as be- 
fore ; or (b) by varying the voltage of the smaller exciting 
dynamo. This latter may be effected either by varying the 
speed of the armature, or by varying the strength of the 
magnetic field, by regulating the strength of the magnet- 
izing current flowing in the field coils by means of a hand 
regulator. It is, however, usual to provide the field circuit 
of each individual dynamo with a hand regulator, so that its 
pressure may be adjusted independently of the others. 

Hand regulators when applied to the regulation of dyna- 
mos, consist of multiple contact switches, so arranged that 
either the resistance of the field magnet circuit may be 
varied, by inserting or removing resistance in series with the 
latter, or one or more of the exciting coils may be cut into or 
out of circuit, or short circuited. ' When arranged for per- 
forming the former operation, the regulator is usually com- 
bined with a set of resistance coils. 

A combination of this description being illustrated in Fig, 
94. It consists of two cast-iron end frames, rigidly connected 
together by means of two iron rods bolted into the ends of 
the frames. The two end frames are hollow, and each con- 



NEW CATECHISM OF ELECTRICITY. 



IQ9 



Fig. 94. 



REGULATING DYNAMOS. 

tain a slate slab, securely fixed in place by means of screws or 
bolts passing through the slabs, and screwing into the iron 
frames. The projecting edges of the slate slabs are provided 
with a number of brass studs or bolts, 
on to which are fixed the ends of spiral 
coils of German silver, platinoid, or 
iron wire. These spiral coils are all 
joined in series, being formed of a con- 
tinuous length of wire, which passes 
up and down between the slate slabs. 
The connections of the spiral coils to 
the external circuit are made by means 
of two terminals, and a number of 
contacts fixed in the slate slab, in the 

f^-l f jj i' i." i" ±" r a' * : J, '*^l bottom end frame. The terminal 
""" V\( ^ shown on the left of the figure is con- 
nected to the extreme left hard spiral 
coil, the terminal on the right being 
connected to the lever of the multiple contact switch or regu- 
lator, shown at the bottom of the figure. This is composed of 
twelve contacts, each contact being electrically connected to 
the bottom j unction of a spiral coil. By altering the position 
of the lever of the regulator the coils can be cut in or out of 
circuit, and the resistance varied, as may be required. When 
the regulator is arranged for performing the latter operation, 
the switch is not combined with a resistance, but the exciting 
coils of the field magnets are divided up into groups, and the 
ends are connected to the contacts or terminals in place of the 




NEW CATECHISM OF ELECTRICITY. 



REGULATING DYNAMOS. 

resistance coils, so that by varying the position of the lever 
each of the exciting coils may be cut into or out of circuit, 
and the strength of the magnetic field adjusted accordingly. 

Regulating Series Dynamos. — The series dynamo is ordi- 
narily used for operating series arc lamp circuits, and for the 
electric transmission of power, its regulation being effected 
by any of the following methods : 

(i) Variation of strength of magnetic field. 

(2) Variatiou of speed of armature. 

(3) Variation of position of brushes on commutator. 

(1.) Regulation by Variation of Strength of Magnetic 
Field. — Although theoretically there are several different 
methods of varying the strength of the magnetic field of a 
series dynamo, in practice, the method of shunting the ex- 
citing current in the field coils is invariably followed. The 
essential principle of this method consists in establishing a 
shunt of variable resistance across the field coils, so that a 
portion of the armature current is shunted through the resis- 
tance, the remainder being used for exciting the field mag- 
nets. The strength of the magnetic field being proportional 
(within certain limits) to the strength of the magnetizing 
current flowing in the exciting coils, it follows that the E. M. 
F. of the machine will vary in proportion to the resistance of 
the shunt. By reducing the resistance of the latter, a larger 
proportion of the total current will flow through it, and the 
strength of the current flowing in the field coils being thus 
reduced, the voltage of the machine will be reduced also, or 



NEW CATECHISM OF ELECTRICITY. 



REGULATING DYNAMOS. 

vice versa. The alteration in the resistance of the shunt can 
be effected by hand, with the aid of a rheostat or hand regu- 
lator, similar in principle to that represented in Fig. 96. 
When used for this purpose, however, the hand regulator is 
usually so arranged that all the resistance coils can be cut 
out of circuit, and the field coils short-circuited thus allow- 
ing of the voltage of the machine being adjusted from zero to 
the maximum value. 

Automatic Regulation. — In cases where an approximately 
constant current is to be maintained in a circuit, as in series 
arc circuits, the adjustment of the resistance of the variable 
shunt is, as a rule, effected automatically by means of some 
electro-magnetic device, actuated by solonoids placed in the 
main circuit. 

Regulation by Variation of Speed of Armature. — The vol- 
tage and output of series dynamos can be governed to some 
extent by varying the speed of the armature, by opening or 
closing the stop-valve of the steam engine, or other motor 
driving the dynamo. This method of regulation is, however, 
only applicable in cases where the fluctuations of the load 
are small, since it involves constant attendance on the* en- 
gine. 

Regulation by Variation of Position of Brushes on Com- 
mutator. — In both ring and drum armatures, when rotating 
in a bi- polar field, there are two points situated at opposite 
extremities of a diameter of the commutator, at one of 
which the potential is a maximum, and at the other a mini- 



NEW CATECHISM OF ELECTRICITY. 



Fig. 




^Ss2 



THE TROY (N. Y.) MACHINE. 



NEW CATECHISM OF ELECTRICITY. 203 

REGULATING DYNAMOS. 

mum, and it is at these points that the brushes must be 
placed, in order to obtain the greatest difference of pressure. 

From the point of maximum potential to the point of mini- 
mum potential either way round the commutator, the pres- 
sure gradually decreases in value. Hence, if the brushes 
make contact at points on the commutator other than the 
neutral points or points of highest and lowest potential, the 
pressure between the brushes will vary in proportion to their 
distance from the neutral points, increasing as they approach 
the neutral points, and decreasing as they recede from them, 
until when making contact at points situated at about 90 
from the neutral points, they will be at nearly the same po- 
tential. 

From this it follows that by merely rocking the brushes 
round the commutator, the pressure at the terminals of the 
machine may be varied and regulated as required. Such a 
method of regulation cannot, however, be used with advan- 
tage in ordinary dynamos, owing to the very destructive 
sparking which takes place at the brushes when they are 
moved any considerable distance from the neutral points. 

Special dynamos have been designed to meet the special 
requirements of this method of regulation, and in which the 
sparking at the brushes is obviated at all loads within the 
range of the machine, but as these have not come into gene- 
ral use they need not be further considered here. 

Regulation of Shunt Dynamos. — In parallel incandescent 
lighting, it is absolutely necessary to maintain the pressure 



204 NEW CATECHISM OF ELECTRICITY. 

REGULATING DYNAMOS. 

at the lamps at a constant value. When the lamps are situ- 
ated at a considerable distance from the machine, as in town 
lighting, this necessitates a constantly varying pressure at 
the machine in order to make up for the fall of pressure in 
the mains connecting the machine to the lamps, which fall is 
dependent on the amount of current flowing in the mains. 
The ease with which this variation of pressure can be effected 
in the shunt dynamo causes this class of machine to be ordi- 
narily used in central stations for incandescent lighting, the 
regulation being effected by either of the following methods, 
or by both in conjunction : (i) Variation of strength of 
magnetizing current. (2) Variation of speed of armature. 

(1.) Regulation by Variation of Strength of Magnetizing 
Current.— This is the only thoroughly efficient method of 
regulation for a shunt dynamo. The variation in the 
strength of the magnetizing current is effected by means of a 
hand regulator or rheostat, similar to that represented in Fig. 
94, which is inserted in the shunt circuit of the machine, as 
shown diagramatically in Fig. 96. In this system of regula- 
tion, the resistances of the field magnet shunt windings and 
of the regulator coils are so proportioned that, when no load 
is on the dynamo, and all the coils of the regulator are in cir- 
cuit with the shunt, the machine generates the normal pres- 
sure required at the lamps. As more and more lamps are 
switched on, the voltage at the lamps has a tendency to 
decrease, and therefore the pressure at the machine must be 
raised in proportion. This is effected by moving the lever of 
the regulator (r), so that fewer resistance coils- are included 



NEW CATECHISM OF ELECTRICITY. 



205 



REGULATING DYNAMOS. 

in the shunt circuit ; the resistance of the latter being thus 
decreased, the exciting current and voltage of the machine is 
increased correspondingly. This method of regulation is 
common with all in which resistances are included in the cir- 
cuit, wastes energy to a certain extent, but the quantity so 

Fig. 96. 




REGULATION FOR A SHUNT-DYNAMO. 



wasted is so small in proportion to the whole that it may be 
considered as of little moment, especially when the advan- 
tages of the system are taken into account. 

Regulation by Variation of Speed of Armature. — A much 
less satisfactory method of regulation for shunt dynamos is 
that of varying the speed of the armature. For small varia- 



206 NEW CATECHISM OF ELECTRICITY. 



REGULATING DYNAMOS. 
tions of pressure, the alteration of speed can be readily 
effected by means of an adjustable governor, the speed of the 
armature being varied by increasing or diminishing the ten- 
sion of the governor spring, according to the pressure required 
at the terminals of the machine. For larger variations, how- 
ever, the only effective method of regulation is by means of 
the stop-valve ; that is to say, the main stop-valves of the 
engines are opened or closed in proportion to the pressure re- 
quired. 

When a number of dynamos are running in parallel, the 
disadvantages of this system, as compared with the method 
of varying the strength of the magnetic field, become 
especially prominent, since, in place of a number of easily 
adjusted hand regulators, fixed in some central position, 
and operated by a single attendant, this method involves 
the regulation being effected by probably as many men as 
there are engines, each regulating the stop- valve of a particu- 
lar engine. Furthermore, the regulation is not nearly so 
effective, owing to the difficulty of expeditiously adjusting the 
valves to give the pressure required. In connection with this 
particular system of regulation, a special type of voltmeter is 
generally employed, this being of extraordinary large dimen- 
sions, with the index or pointer about 18 inches in length, so 
that its indications may be seen all over the engine-room. 

Regulating Compound Dynamos. — A carefully com- 
pounded dynamo will, when run at the speed for which 
it was designed, regulate itself perfectly, and maintain a con- 
stant difference of potential at its terminals under any varia- 



NEW CATECHISM OF ELECTRICITY. 20? 

REGULATING DYNAMOS. 

tion of load within its range. In practice, however, it is not 
always possible to work a dynamo under these exact condi- 
tions, and, moreover, in the case of large machines,' the effect 
of temperature upon the resistance of* the machine has ari 
appreciable effect upon the voltage. 

Means for regulating the latter are desirable. The voltage 
may be varied to a certain extent by suitably adjusting the 
governor of the driving engine, increasing or decreasing the 
speed ; but in many cases this is not very desirable or possible, 
and a much better method of obtaining the desired variation 
of voltage is to insert a variable resistance or hand regulator 
in the shunt circuit of the machine, the resistance of the 
shunt being suitably proportioned to give the requisite margin 
for regulation. 

Regulating Over-Compounded Dynamos, — It is sometimes 
desirable, as in central light and power stations, to have a 
dynamo which will maintain a constant pressure at a point 
some distance from the machine. In this case the dynamo is 
over-compounded, or the series coils are wound with a greater 
number of turns, in order to raise the pressure at the termi- 
nals of the machine as the load increases, and thus compen- 
sate for the fall of pressure in the mains. 

As it is well to vary the degree of over-compounding, the 
series coils of such dynamos are usually so proportioned as to 
give from 10 per cent, to 20 per cent, of over- compounding, 
and a strip or ribbon of German silver or copper is arranged 
as a shunt to the series coils. By suitably including a greater 



208 



NEW CATECHISM OF ELECTRICITY. 



Fig. 97. 




AN AI/TERNATOR. 



NEW CATECHISM OF ELECTRICITY. 200, 

REGULATING DYNAMOS. 

or lesser length of ribbon in the circuit, the resistance of the 
variable shunt and the amount of current flowing in the 
series coils can be varied, and the percentage of over-com- 
pounding adjusted accordingly. 

Regulation of Motors. — It is extremely important that 
electric motors should be so arranged as to run at a uniform 
speed, no matter what their load may be. For example, in 
driving lathes, and many other kinds of machinery, it is 
essential that the speed should be regular, and that the motor 
should not "race " as soon as the stress of the working load is 
removed. 

It will be evident that the employment of certain combina- 
tions for the field magnets, under the condition of a constant 
potential, when driven at a constant fpeed, regulate the 
dynamo. 

Now it is not hard to see that this problem may be applied 
conversely, and that motors may be built with a combination 
of arrangements for their field-magnets, such that, when sup- 
plied with currents under the standard condition of constant 
potential in the distributing mains, their speed shall be con- 
stant whatever the load. It will be evident that the windings 
must oppose one another— one must tend to demagnetize the 
field magnet, the other to magnetize. 

This effect is based upon the important electrical law that 
if a current is passed through a dynamo the armature will 
rotate. In all cases the rotation is in such a direction as to 
induce in the armature an electro-motive force opposed to that 
of the driving current. 



2IO 



NEW CATECHISM OF ELECTRICITY. 



Fig. 98. 




four pole; ring dynamo. 



NEW CATECHISM OF ELECTRICITY. 



COUPLING OF DYNAMOS. 



When it is needful to generate a large and variable 
amount of electrical energy, as is the case in large installa- 
tions and central generating stations, apart from the question 
of liability to breakdown, it is neither economical or desir- 
able that the whole of the energy should be furnished from a 
single dynamo. Since the efficiency of a dynamo is depends 
ent upon its output at any moment, or the load at which it is 
worked, the efficiency varying from 95 per cent, at full load 
to 80 per cent, at half load, it is obviously advisable in order 
to secure the greatest economy in working, to operate any 
dynamo as far as possible at full load. Under the above cir- 
cumstances, when the whole of the output is generated by a 
single dynamo this can evidently not be effected, for the load 
will naturally fluctuate up and down during the working 
hours, as the lamps, motors, etc., are switched into and out 
of circuit ; and hence, although the dynamo may be working 
at full load during a certain portion of the day, at other times 
it may probably be working below half load, and therefore 
the efficiency and economy in working in such an arrange- 
ment is very low. In order to secure a maximum efficiency ^ 
it is usual in such cases to divide up the generating plant into 
a number of units, varying in size, so that as the load fluctu- 



NEW CATECHISM OF ELECTRICITY. 



COUPLING OF DYNAMOS. 

ates it can either be shifted from one dynamo to another as 
the exigencies of the case requires ; or when the load exceeds 
the capacity of the largest dynamo in the plant, the output of 
one can be added to that of another, and thus the dynamos 
actually at work at any moment can be operated as nearly as 
possible at full load. As it is necessary to take certain pre- 
cautions in ccnnecting one dynamo to another, in order that 
the other dynamos may not be affected by the change, and 
that they may work satisfactorily together, it is well to 
consider these in connection with the different types of 
machines. 

Series and Parallel Connections, — Since the output of a 
dynamo is made up of two factors, viz. : the pressure and the 
current respectively, it follows that the output of a machine 
may be increased by increasing either the one or the other, or 
both at the same time. As, however, the systems of distri- 
bution in use at the present time involve the maintenance of 
either a constant current or a constant pressure in a circuit, 
the methods of coupling dynamos together resolve them- 
selves into two kinds, corresponding to the systems of distri- 
bution, viz.: parallel and series connections. In coupling 
two or more machines in parallel, the pressures of all the ma- 
chines are kept at a constant value, while the output of the 
plant is increased in proportion to the current capacities of 
the machines in circuit. In the series coupling, the current 
capacity of the plant is kept at a constant value, while the 
output is increased in proportion to the pressures of the ma- 
chines in circuit. 



NEW CATECHISM OF ELECTRICITY. 



213 



COUPLING OF DYNAMOS. 

Shunt Dynamos in Series.— The simplest operation in con- 
nection with, the coupling of dynamos, and the one used 




probably more frequently in practice than any other, is the 
coupling of two or more shunt dynamos to run either in 



214 NEW CATECHISM OF ELECTRICITY. 



COUPLING OF DYNAMOS. 

series or in parallel. When connected in series, the positive 
terminal of one machine is joined to the negative of the 
other, and the two outer terminals are connected through the 
ammeter A, fuses F x F 2 , and switch S, to the two main con- 
conductors or omnibus bars as represented in Fig. 99. The 
machine will operate when the connections are arranged in 
this manner, if the ends of the shunt coils are connected to 
the terminals of the respective machines ; but a better plan 
is to put both the coils in series with one another, so that they 
form one long shunt between the two main conductors, as 
shown in Fig. 99. When arranged in this way, the regula- 
tion of both machines may be effected simultaneously by 
inserting a hand regulator (r) in series with the shunt circuit, 
as represented. 

Shunt Dynamos in Parallel. — The coupling of two or 
more shunt dynamos to run in parallel is effected without 
any difficulty, and is probably an operation more frequently 
performed than any other, it being daily practiced in central 
generating stations on the low tension system. Fig. 100 illus- 
trates diagramatically the method of arranging the connec- 
tions. The positive and negative terminals of each machine 
are connected respectively to two massive insulated copper 
bars, shown at the top of the diagram, and called omnibus 
bars, through the double pole switches S x S 2 , and the double 
pole fuses F x F 2 . Ammeters, A x A 2 , are inserted in the 
main circuit of each machine, and serve to indicate the 
amount of current generated by each. An automatic switch 
or cutout, AC X AC 2 , is also shown as being included in the 



NEW CATECHISM OF* ELECTRICITY. 



215 



COUPLING OF DYNAMOS. 

main circuit of each of the machines, although this appli- 
ance is sometimes dispensed with. The pressure of each of 






H 



the machines is regulated independently by means of the 
hand regulators R x R 2 , inserted in series with the shunt cir- 
cuit. 



216 NEW CATECHISM OF ELECTPICITY. 

COUPLING OF DYNAMOS. 

The shunt circuits are represented as being connected to 
the positive and negative terminals of the respective ma- 
chines, but in many cases, where the load is subjected to sud- 
den variations, and when a large number of machines are 
connected to the bus bars, the shunt coils are frequently con- 
nected direct to these ; and in such circumstances this method 
is preferable, as by means of it the fields of the idle dynamos 
can be excited almost at once direct from the bus bars by the 
current from the working dynamos, and hence if a heavy load 
should come on suddenly, no time need be lost in building up 
a new machine previous to switching it into parallel. The 
pressure of the lamp circuit is given by a voltmeter, whose 
terminals are placed across the omnibus bars ; and the pres- 
sure at the terminals of each of the machines is indicated by 
separate voltmeters or pilot lamps, the terminals of which are 
connected to those of the respective machines. 

Switching Dynamo into and out of Parallel. — In order to 
put an additional dynamo into parallel with those already 
working, it is necessary to run the new dynamo up to full 
speed, and, where it excites, regulate the pressure by means 
of a hand regulator until the voltmeter connected to the 
terminals of the machines registers one or two volts more 
than the voltmeter connected to the lamp circuit, and then 
close the switch. The load upon the machine can then be 
adjusted to correspond with that upon the other machines by 
means of the hand regulator. In this class of machine there 
is little or no danger of overloading an armature when con- 
necting it to the bus bars, and therefore the pressure need not 



NEW CATECHISM OF ELECTRICITY. 21 7 

COUPLING OF DYNAMOS. 

be adjusted with very great accuracy ; in fact, it is common 
practice in central stations to judge of the voltage of the new 
dynamo merely by the appearance of its pilot lamp. 

When shutting down a machine, the load or current must 
first be reduced, by gradually closing the stop-valve of the 
engine, or inserting resistance into the shunt circuit by means 
of the hand regulator ; then when the ammeter indicates nine 
or ten amperes, the main switch is opened, and the engine 
stopped. By following this plan, the heavy sparking at the 
switch contacts is avoided, and the tendency for the engine 
to race reduced. Great care, however, has to be taken that 
the current is not reduced too far, or otherwise there is a risk 
of the machine being stopped, receiving a back current from 
the other dynamos, resulting in heavy sparking at the com- 
mutator, and in the machine being driven as a motor. To 
obviate this danger, and to render these precautions needless, 
shunt dynamos when running in parallel are frequently pro- 
vided with automatic cutouts, set so as to automatically switch 
out the machine when the current falls below a certain mini- 
mum value. 

Dividing Load. — If a plant composed of shunt dynamos 
running in parallel be subjected to variations of load, gradual 
or instantaneous, the dynamos will, if they all have similar 
characteristics, each take up an equal share of the load ; if, 
however, as is sometimes the case, the characteristics of the 
dynamos are dissimilar, the load will not be shared equally ; 
the dynamos with the most drooping characteristics taking 
less than their share with an increase of load, and more than 



2l8 NEW CATECHISM OF ELECTRICITY. 

COUPLING OF DYNAMOS. 

their share with a decrease of load. If the difference is slight, 
it may readily be compensated by means of the hand regula- 
tor increasing or decreasing the pressures of the machines, as 
the load varies or fluctuates. If, however, the difference is 
considerable, and the fluctuations of load very rapid, it be- 
comes practically impossible to evenly divide the load by 
this means so that each dynamo takes up its proper share of 
the work. 

Under such circumstances, the pressure at the bus bars is 
liable to great variations, and there is also great liability 
for the fuses of the overloaded dynamos to be blown, thus 
precipitating a general breakdown. To cause an equal divis- 
ion of the load amongst all the dynamos, under such circum- 
stances, it is needful to insert a small resistance in the 
armature circuits of such dynamos as possess the straightest 
characteristics, or of such dynamos as take more than their 
share of an increase of load. By suitably adjusting or pro- 
portioning the resistances, the pressures at the terminals of 
all the machines may be made to vary equally under all varia- 
tions of load, and each of the machines will then take up its 
proper share of the load. 

Automatic Cutouts. — Shunt and other dynamos are always 
liable when working to have the pressure at their terminals 
reduced, either through a fault in the armature or field cir- 
cuits, or through a hot bearing or other cause. When a num- 
ber of shunt dynamos are running in parallel, and the 
pressure of one falls below that of the others, the load is 
transferred from the machine having the lower pressure to 



NEW CATECHISM OF ELECTRICITY. 



2ig 



Fig. 101. 



COUPLING OF DYNAMOS. 

the machine with the higher pressure, until when the pres- 
sure falls below a certain minimum value a reverse current is 
sent through the armature of the machine whose pressure has 
been reduced by the machines having the higher pressure. 

This results in the 
machine being driven as 
a motor, and in great 
sparking at the commuta- 
tors of all the dynamos, 
and also in an overload of 
the driving dynamos, and 
probably in the blowing 
out of all the fuses. In 
order to prevent this 
occurring, shunt dynamos 
when running in parallel 
are each as a rule provided 
with an automatic switch, 
placed between one or 
both of the machine ter- 
minals and the omnibus 
bars, whose duty it is to switch off automatically the machine 
in the event of a reduction of its voltage from any of the 
above-mentioned causes. The principle and action of this 
instrument will be understood by reference to Fig. 101. 
Briefly described, the instrument consists of an electro-magnet, 
fixed upon a slate base, and shown in the upper portion of the 
figure, and an iron armature fixed to the ends of the pivoted 
levers of the switch, shown in the lower portion of the figure. 




AUTOMATIC SWITCH. 



220 NEW CATECHISM OF ELECTRICITY. 

COUPLING OF DYNAMOS. 

The electro-magnet is included in series with the switch 
and armature circuit, and while the pressure of the machine 
to which the instrument is connected remains at its normal 
value, the current flowing in its coils Is sufficiently strong to 
enable it to hold up the iron armature against its pole pieces. 
If from any cause the voltage of the machine is reduced, the 
current flowing in its armature is decreased also, until when 
it falls below a certain minimum value at which the automatic 
switch is arranged to act, the strength of the electro-magnet 
has been so far diminished that it can no longer hold up the 
armature against the weight of the levers, and these latter 
therefore drop and switch the machine out of circuit. A 
fusible cutout is shown in the centre of the figure, which, 
when the current exceeds the safe capacity of the machine, 
melts, and cuts out the armature, thus saving it from destruc- 
tion. , 

Coupling Series Dynamos in Series. — Series wound dyna- 
mos will run satisfactorily together without special precau- 
tions when coupled in series, if the connections are arranged 
as in Fig. 102. The positive terminal of one dynamo is con- 
nected to the negative terminal of the other, and the two 
outer terminals are connected directly to the two main con- 
ductors or bus bars through the ammeter A, fuse F, and 
switch S. If it be desired to regulate the pressure and out- 
put of the machines, variable resistances, or hand regulators 
R L R 2 , may be arranged as shunts to the series coils, as 
represented, so as to divert a portion or the whole of the cur- 
rent therefrom. 



NEW CATECHISM OF ELECTRICITY. 



221 



COUPLING OF DYNAMOS. 

Series Dynamos in Parallel. — Simple series wound dyna- 
mos not being well adapted for the purpose of maintaining a 




^"^^^^ 








o _^^> 








O 


oS 


***^^*^ 












<N 






O 




6 




H 



el 

or 



constant pressure, are seldom in practice coupled in parallel ; 
the conditions of working, however, derive importance from 



222 NEW CATECHISM OF ELECTRICITY. 



COUPLING OF DYNAMOS. 

the fact that compound dynamos, being provided with series 
coils, are subject to similar conditions when working in 
parallel, which is frequently the case. In coupling two or 
more plain series dynamos in parallel, the same procedure 
cannot be followed as in the case of plain shunt dynamos, for 
the reason that if the voltage of the new dynamo is exactly 
equal to that of the bus bars when connected in parallel, the 
combination will be unstable. If from any cause the pres- 
sure at the terminals of one of the dynamos falls below that 
of the others, it immediately takes a smaller proportion of 
the load ; as a consequence, the current in its field coils is at 
once reduced, and a further fall of pressure immediately 
takes place owing to this circumstance. This increased fall 
of pressure again causes the dynamo to relinquish a portion 
of its load, and again occurs a further fall of pressure. Thus 
the process goes on, until finally the dynamo ceases to supply 
current, and the current from the other dynamos flowing in 
its field coils in the reverse direction reverses its magnetism, 
and causes it to run as a motor against the driving power in 
the opposite direction to that in which it previously ran as a 
dynamo. 

Under such circumstances the armature is liable to be 
destroyed if the fuse is not immediately blown, and in any 
case is subjected to a very detrimental shock. This tendency 
to reversal in series dynamos can be effectually prevented by 
the simple expedient of connecting the field coils of all the 
dynamos in parallel, as was first suggested by Gramme. 
This is effected in practice by connecting the ends of all the 



NEW CATECHISM OF ELECTRICITY. 



223 



series coils where they join on to the armature circuit by a 
third connection, called the " equalizing connection," or 
" equalizer,' ' as shown in Fig. 103. The immediate effect of 




o 

H 




2 24 NEW CATECHISM OF ELECTRICITY. 



COUPLING OF DYNAMOS. 

this equalizing connection is to cause the whole of the cur- 
rent generated by the plant to be divided among the series 
coils of the several dynamos in the inverse ratio of their 
resistance, without any regard as to. whether this current 
comes from one armature, or is divided 'among the whole. 
The fields of the several dynamos being thus maintained 
constant, or at any rate caused to vary equally, the tendency 
for the pressure of one dynamo to fall below that of the 
others is much diminished, reversal of polarity is entirely ob- 
viated, and the machines will run together under all condi- 
tions of load. 

Coupling Cotnpound Dynamos in Series. — Since compound 
dynamos may be regarded as a combination of the shunt and 
series wound machines, and as no special difficulties are ex- 
perienced in running these latter in series, analogy at once 
leads to the conclusion that compound dynamos under similar 
circumstances may be coupled together with equal facility. 
This is found to be the case in practice, it being only neces- 
sary, in order that two compound dynamos may run satisfac- 
torily together in series, to connect the series coils of each 
together, as represented in Fig. 102 ; the shunt windings must 
be connected as a single shunt, as in Fig. 99, which may 
either extend simply across the outer brushes of the ma- 
chines, so as to form a double short shunt, or may be a shunt 
to the bus bars or external circuit, so as to form a double 
long shunt. 

Compound Dynamos in Parallel. — Compound dynamos 
will not run satisfactorily together in parallel, unless all their 



NEW CATECHISM OF ELECTRICITY. 



225 



COUPLING OF DYNAMOS. 

series coils are connected together by an equalizing connec- 
tion, as in series dynamos. The method of arranging the 
connections as adopted in practice, being illustrated in Fig. 
104. By means of it idle machines are completely discon- 




SHUNT COILS 

vvwwvw 



Fig. 104. 



nected from those at work. The reference letters indicate as 
follows — S x S 3 are switches ; F x F 3 fuses ; A x A 3 are amme- 
ters, which indicate the total amount of current generated by 
each of the machines; ACj AG 3 are automatic switches, ar- 



226 



NEW CATECHISM OF ELECTRICITY. 



Fig. 105. 



COUPLING OF DYNAMOS. 

ranged for automatically switching out a machine in the 
event of the pressure at its terminals being reduced through 
any cause ; R x R 2 are hand regulators, inserted in the shunt 
circuits of each of the machines, by means of which the: 
pressures of the individual machines may be varied and the: 
load upon each adjusted. The pressure at the bus bars is. 
given by the voltmeter V, one terminal of which is connected 

to each of the bars ; a second 
voltmeter may be used, to give 
the pressure of any individual 
machine, by connecting ' Volt- 
meter keys ' ' to the terminals of 
each of the machines, or a sepa- 
rate voltmeter may be used for 
each individual machine. The 
equalizer is connected direct to 
the positive brushes of all the 
dynamos, a switch being fitted 
for disconnecting it from the 
circuit when the machine to which it is connected is not 
working. In connection with this arrangement the form of 
switch shown in Fig. 105 is generally used. This consists of 
three contacts, insulated from each other, and fixed upon a 
slate base ; the two contacts at the sides are respectively 
connected to the positive and negative conductors, while the 
central contact is connected to the equalizer. The circuits are 
opened or closed simultaneously by means of three levers, 
which are forced between the contacts by the handle. These 




AUTOMATIC SWITCH. 



NEW CATECHISM OF ELECTRICITY. 227 

COUPLING OF DYNAMOS. 

levers are each provided with removable knife contacts for 
taking the spark at breaking contact, and are insulated from 
each other, and rigidly fixed upon a spindle which is capable 
of a small angular movement in the bearings, shown in the 
lower part of the figure. 

Switching a new machine into Parallel. — If the charac- 
teristics of all the dynamos are similar, and the connections 
are arranged as in Fig. 101, page 225, the only precaution 
to be observed in switching a new machine into parallel is to 
have its voltage equal, or nearly equal, to that of the bus 
bars previous to closing the switch. If this is the case, the 
new machine will instantly take up its due share of the load 
without disturbance or shock of any kind. If a dynamo is 
to be cut out of circuit, it will first be necessary to reduce the 
load to a few amperes, as in the case of shunt dynamos, either 
by easing down the engine, or by cutting resistance into the 
shunt circuit by means of the hand regulator, and then open 
the switch. Previous to this, however, it is advisable to in- 
crease the voltage at the bus bars to a slight extent, as while 
slowing down the engine the load upon the outgoing dynamo 
is transferred to the other dynamo armatures, and the current 
in their series coils not being increased in proportion the 
voltage at the bus bars is consequently reduced somewhat. 

Equalizing Load. — When a number of compound dynamos 
of different outputs, size, or make are running together in 
parallel, it frequently happens that all their characteristics 
are not exactly similar, and therefore the load is unequally 
distributed amongst them, some being overloaded, whilst 



228 NEW CATECHISM OF ELECTRICITY. ■ 

COUPLING OF DYNAMOS. 

others do not take up their proper share of the work. If the 
difference is small, it may be compensated by means of the 
hand regulator ; if large, however, other means must be 
taken to cause the machines to take up their due proportion 
of the load. If the series coils of the several dynamos are 
provided with small adjustable resistances, in the form of 
German silver or copper ribbon inserted in series with the 
coils, the distribution of the current in the latter may be 
altered by varying the resistance attached to the individual 
coils, and thus the effect of the series coils upon the indi- 
vidual armatures in raising the pressure may be adjusted, and 
the load thus evenly divided among the machines. 



SYMBOLS, ABBREVIATIONS AND 
DEFINITIONS. 



QuKS. What is the meaning of the term l ' dialectrics ' ' ? 

Ans. It means the same as the word " non-conductor." 
Faraday gave the name dielactrics to what we call non-con- 
ductors. 

QuKS. What is "a booster" ? 

Ans. It is by this term that a dynamo is called which is 
arranged for use in an Edison incandescent light system to 
raise the pressure in a place where it is needed. 



Note. — See pages 114 and 195. 



NEW CATECHISM OF ELECTRICITY. 220. 

SYMBOLS, ABBREVIATIONS AND DEFINITIONS. 

QuKS. What does the letter " F" stand for? 

Ans. It is an abbreviation for Fahrenheit, as 10 F., 
meaning io° Fahrenheit ; or io° — io° meaning ten degrees 
below zero. 

The Fahrenheit scale is in nse in the United States and 
England ; upon it the temperature of melting ice is (32 °) 
thirty-two degrees ; that of condensing steam 180 F. 

QuES. What are Foucault- currents ? 

Ans. These are the same as eddy currents, elsewhere 
explained and illustrated. 

QuKS. What is the meaning of the word " deflection r% ? 

Ans. This is the movement out of the magnetic plane, 
due to disturbance by or attraction towards a mass of iron or 
other magnet. 

QuES. What is the meaning of the term "make and 
break"? 

Ans. It describes a current which is continually broken 
and started again. It is applied only where the " makes " and 
the "breaks " succeed each other with great rapidity. 

Quks. What do the letters "B. W. G." express? 

Ans. This is an abbreviation of Birmingham Wire Guage. 

QuKS. What is the meaning of " B. & S." ? 

Ans, These are abbreviations of "Brown & Sharp" 
(American Guage). 



230 



NEW CATECHISM OF ELECTRICITY. 




MULTIPOLAR DYNAMO. 



NEW CATECHISM OF ELECTRICITY. * 23I 



FAULTS IN ARMATURES. 



The armature and commutator are the most vulnerable 
parts of a dynamo, and being subjected whilst rotating to 
various detrimental influences, are a prolific source of faults, 
the chiefest of which may be enumerated as follows : 

(1) Short circuits in armature. 

(2) Grounds in armature. 

(3) Disconnections in armature circuit. 

(4) Flats on commutator. 

(5) Short circuits in commutator, 

(6) Rough and uneven surface of commutator. 

(7) Segments loose or knocked in. 

(1.) Short Circuits in Armatures. — The classes of short 
circuits which occur in the armature are — (a) Short circuits in 
individual sections or coils ; (b) Short circuits between adja- 
cent coils ; (c) Short circuits between sections through frame 
or core of armature ; (d) Short circuits between sections 
through binding wires ; (e) Partial short circuits in arma- 
ture. • 



232 NEW CATECHISM OF ELECTRICITY. 

FAULTS IN ARMATURES. 

(a) Short Circuits in Individual Sections or Coils, — This 
is an exceedingly common fault, which makes its presence 
known by a violent heating of the armature, flashing at the 
commutator, flickering of the light, and by a smell of burn- 
ing varnish or overheated insulation. When these indications 
are present, the machine should be stopped at once, otherwise 
the armature is liable to be burnt out. The fault is due 
either to metallic dust lodging in the insulation between ad- 
jacent bars of the commutator, or to one or more convolutions 
of the coils coming into contact with each other, either 
through a metallic filing becoming embedded in the insula- 
tion or damage to the insulation. When the machine is 
stopped, the faulty coil, if not burnt out, can generally be 
located by running the fingers over the armature, by its ex- 
cessive temperature over the rest of the coils, and by the 
baked appearance of the varnish or insulation. If the ma- 
chine will not build, and it is suspected that the fault arises 
from short circuited armature coils, the field magnets should 
be excited by the current from a storage battery or another 
dynamo, and having raised the brushes from contact with 
the commutator, the armature should be run for a short time. 
In stopping, the faulty coil or coils may be located by the 
heat generated by the short circuit. When the dynamo is 
started to localize a short circuit, great precautions should be 
taken, and the machine only run for a few minutes at a time 
until the faulty coil is detected. A short circuited coil may 
also be located by the fall of potential method. Fig. 107 
illustrates diagramatically this method of testing. Discon- 



NEW CATECHISM OF ELECTRICITY. 



233 



FAULTS IN ARMATURES. 

nect the external and field circuits from the armature, and 
pass a large current — say from 20 to 100 amperes — from a 




Fig. 107. 

battery (b) or another dynamo through the whole armature 
by means of the brushes. Then, having previously well 



234 NEW CATECHISM OF ELECTRICITY. 

FAULTS IN ARMATURES. 

cleaned the commutator, measure the difference of potential 
between adjacent segments all round the commutator (c), by 
means of a voltmeter or galvanometer (g), the terminals of 
which are connected to adjacent segments, as shown. 

The short circuited coil or coils will be located by the 
difference of potential between the corresponding segments 
being little or nothing. It may be remarked, however, that this 
is not always a decisive test. In some cases the short circuit 
may be intermittent, or may disappear as soon as the armature 
ceases to rotate. In such cases, the short circuit is caused by 
the wire coming into contact through the action of the cen- 
trifugal forces developed by the rotation of the armature. 

The former test is therefore the more reliable in all cases. 
When the faulty coil has been located, the insulation between 
the segments of the commutator to which its ends are con- 
nected should be carefully examined for anything that may 
bridge across from plate to plate, and scraped clean from any 
adherent metallic particles or burrs. If the commutator is 
apparently all right, the fault probably lies in the winding. 
The insulation of this should be carefully examined, and any 
metallic filing or other particle discovered therein carefully 
removed, and a little shellac varnish applied to the faulty 
part. 

It will sometimes happen that a small portion of the 
insulation has been abraded from two adjacent conductors, 
thus causing them to come into electrical contact with each 
other. In such circumstances a small boxwood or other 



NEW CATECHISM OF ELECTRICITY. 



235 



Fig. 108. 




ELECTRIC HOISTING MACHINE. 



236 NEW CATECHISM OF ELECTRICITY. 

FAULTS IN ARMATURES. 

hardwood wedge, coated with shellac varnish, and driven in 
tightly between the wire, will generally effect a cure. If the 
faulty coil cannot be expeditiously repaired, and the dynamo 
is urgently wanted, the coil may be cut out of circuit alto- 
gether, and the corresponding commutator segments con- 
nected together with a piece of wire, of a size proportionate 
to the amount of current to be carried, soldered to each. ^ It 
will not be necessary to cut out and remove the entire coil. 

If the active portions only are separated from one another, 
so that they do not form a closed circuit, it will answer the 
purpose — e. g. f if the wires are cut with a chisel at the point 
where they pass over the ends of the core, and the ends sepa- 
rated, it will be quite as effective as removing the entire 
coil. It is wise, of course, to rewind the coil at the first 
opportunity. 

(d) Short Circuits between Adjacent Coils, — Whilst in the 
ring armature the presence of this fault does not necessarily 
imply that the machine will not build, in the drum armature 
wound into a single layer of conductors it entirely prevents 
this occurring. Reference to Fig. 128 will show that adjacent 
coils are during a certain period of the revolution at the full 
difference of potential generated by the machine. Hence, if 
any two adjacent coils are connected together or short cir- 
cuited, the whole of the armature will be practically closed 
on itself, any current generated flowing within the armature 
only, without passing to the external circuit. 

Large drum armatures wound with compressed and stranded 
bars and connectors are particularly susceptible to this fault, a 






NEW CATECHISM OF ELECTRICITY. 237 

FAULTS IN ARMATURES. 

slight blow generally forcing one or more of the strands into 
contact with the adjacent bars, thus short circuiting the arma- 
ture, and rendering it practically useless so far as the genera- 
tion of current is concerned. In this class of short circuit in 
drum armatures, the method of locating the faulty coils by 
exciting the field, and running the armatures on open circuit, 
is not applicable, for the reason that the whole armature 
will be heated equally. Mr. L,oomis, in the Electrical ilngi- 
neer of New York, has described a method of locating faults 
of this description, and, as it appears reliable, it is given 
below: 

" In following this plan, no arrangement for belting need 
be made. It is only necessary to fasten a monkey wrench to 
the rim of the pulley, or, better still, a crank to the shaft. 
Now, excite the fields, and, to make the effects more marked, 
connect the coils in parallel, as the excessive current will only 
be used for a moment. When this has been done the strong- 
est man will scarcely be able to rotate the armature, a ad then 
only with extreme slowness, except at one position. When 
this position has been found, mark the armature at points in 
the centre of the pole pieces (a b), as shown in the accom- 
panying diagram (Fig. 109), and at both ends of the armature. 
The explanation is that both halves of the armature oppose 
one another at this position ; but when not at these points a 
continuous circuit is formed, and the resultant magnetic 
effect is enormous. As the ' cross ' or * short ' circuit will be 
found at one of these four marked points, it becomes desir- 
able to know in which one it is most likely to be found. 



238 



NEW CATECHISM OF ELECTRICITY. 



FAULTS IN ARMATURES. 

Experience has shown that it is nearly always on the com- 
mutator end in the last half of the winding, where the wires 
pass down through the first half terminals. This applies to 
an unequal winding. In armatures where the windings are 
equal, it is as liable to occur at one point as at another. With 
this method a defect can be found and remedied in a few mo- 
ments, for it has always been a simple matter to repair it 

Fig. 109. 




ARMATURE. 

when discovered. These results can be observed in a perfect 
armature by connecting the opposite sections of the commu- 
tator. 



The above will be understood to apply to armatures 
having Siemens winding." Faults of this description can 
frequently be discovered by a careful inspection of the wind- 
ings of the armature without recourse to testing. When 
located, the fault can usually be' repaired with a hardwood 



NEW CATECHISM OF ELECTRICITY. 239 

FAULTS IN ARMATURES. 

wedge, as explained above, or a piece of mica or vulcanized 
fibre cemented in place with shellac varnish. 

(c) Short Circuits between Sections through Frame or Core 
of Armature. — The localization of this fault can be effected 
by the methods described above, and by disconnecting the 
whole of the armature coils from the commutator and from 
each other, and testing each separately with a battery and 
galvanometer coupled up as in Fig. 137, one wire being con- 
nected to the shaft and the other to the end of the coil under 
test. As a rule, there is no way of remedying this fault 
othsr than unwinding the defective coils, reinsulating the 
core, and rewinding new coils. 

(d) Short Circuits between Sections through Binding 
Wires. — This fault is the result of a loose winding, and is 
caused by the insulation upon which the binding wires are 
wound giving way, thus bringing coils at different potentials 
together. As a consequence to the heavy current which 
flows, the binding wires are as a rule unsoldered or burned. 
The location of the fault can therefore be effected by simple 
inspection. To remedy, it will be necessary to unwind and 
rewind on new binding wires, on bands of mica or vulcanized 
fibre, soldering at intervals to obviate flying asunder. 

(e) Partial Short Circuits in Armatures. — This is, as a 
rule, due to the presence of moisture in the windings. To 
remedy, the armature should be taken out and exposed to a 
moderate dry heat, or subjected to a current equal to that 
ordinarily given by the dynamo. Under the action of heat or 



240 



NEW CATECHISM OF ELECTRICITY. 



Fig. 110. 




THE; CINCINNATI MACHINE). 



NEW CATECHISM OF ELECTRICITY. 24 1 

FAULTS IN ARMATURES. 

of this current the moisture will be gradually dispersed. 
When thoroughly dry, and whilst still warm, a coat of shel- 
lac or rubber varnish should be applied to the whole of the 
windings. 

(2.) Grounds in Armatures* 

(a) Armature Coils Grounded or Connected to Core or 
Frame of Armature. — When this fault is confined to a single 
coil, it is not in itself liable to do any damage. If, however, 
a similar fault develops in some other part of the dynamo, or 
in the external circuit, the coil is liable to be burned out. 
Mr. F. Bain, in the Western Electrician, has described a sim- 
ple method of locating a coil grounded to the frame of an 
armature, which is reprinted below. Fig. in clearly shows 
the arrangements of the details. B is a battery or dynamo 
circuit, giving a current of a few amperes through the arma- 
ture by its own brushes (i and 2). At a, a roughly-made 
galvanometer, to carry some 25 amperes or so, is placed, one 
terminal being in connection with the shaft of the armature, 
and the other attached to a movable brush (3). Since the 
function of the particular galvanometer is simply to show a 
deflection when a current is passing, and to mark zero when 
there is none, a coil of thick wire, with a pocket-compass in 
the centre, will do all that is required, but care must be taken 
to remove it sufficiently far away from the disturbing effects 
of the armature magnetism. The manner of testing is as fol- 
lows : 

Assume a steady current to be flowing from battery (b) 
through the armature, touch the commutator with brush (3), 



242 



NEW CATECHISM OF ELECTRICITY. 



FAULTS IN ARMATURES. 

and a current will flow through (g). Slowly rotate the arma- 
ture or the brush (3), until the galvanometer (g) shows no 
deflection. The coil in contact with 3 will be found to be 
grounded or connected to the frame. A hand regulator or 
rheostat (r) may be inserted in series with the battery or dy- 
namo circuit to regulate the strength of the current passing. 



Fig. 111. 





ifr 




B 










— ■ 


.5jt? 


\\& 


s „ 








R 


ogo 








c 


r 







ARMATURK AND RHEOSTAT. 



The main advantage of this test is that the damaged coil 
can be located without unsoldering the coils from the commu- 
tator, which is sometimes a difficult operation without proper 
tools ; and further, the fault can frequently be repaired with- 
out disconnecting any of the wires if its exact position be 
determined. 



NEW CATECHISM OF ELECTRICITY. 243 

FAULTS IN ARMATURES. 

(3.) Disconnections in Armature Circuit. — A partial or 
complete disconnection in the armatnre circuit is always 
characterized by heavy sparking at the commutator, but not, 
as a rule, by an excessive heating of the armature or slipping 
of the belt, and this enables this fault to be distinguished 
from a short circuit. The faulty part can always be readily 
located by the "flat " which it produces upon the surface of 
the commutator. The armature circuit being open at the 
faulty part, heavy sparking results at every half revolution as 
. the brushes pass over it, and as a consequence the correspond- 
ing segments are "pitted" or "flattened" with respect to 
the others, and may easily be discovered on examination. 

The fault may occur in either the commutator or in the coils 
of the armature. To ascertain whether it is in the latter, 
carefully examine the winding of the faulty coil. The defect 
may be sought for more particularly at the commutator end 
of the armature, as breaks in the wire are most frequent 
where the connections are made with the commutator seg- 
ments. If no break can be discerned, try passing a heavy 
current through the faulty coil by means of the brushes. If a 
disconnection exists in sufficient contact to pass a current, the 
coil will be heated in the neighborhood of the disconnection, 
and may be discovered by running the fingers over the coil. 

When located, the fault may be repaired by rewinding 
the coil, or carefully cleaning the broken ends aiid jointing. 
The fault may also be temporarily repaired by soldering the 
adjacent commutator segments together without disconnect- 
ing the coil. 



244 NEW CATECHISM OF ELECTRICITY. 

FAULTS IN ARMATURES. 
(4.) Flats on Commutator. — This is the name given to a 
peculiar fault which develops on one or more bars of the 
commutator. It is not confined to dynamos of bad design or 
construction, but frequently appears on those of the highest 
class, and may be recognized as a " pitting' ' or " flattening ' ' 
of one or more segments. It is always accompanied by 
sparking at the brushes, and may be due to a periodical j ump- 
ing of the brushes, caused by a bad state of the commutator, 
or a bad joint in the driving belt, or to a flaw, or a difference 
in the composition of the metal of the particular bar upon 
which it appears. But more frequently it may be traced to a 
more or less developed fault, such as a disconnection, either 
partial or complete, in the armature coil. The disconnection 
may occur either in the coil itself, or at the point where its 
ends make connection with the lug of the commutator, or at 
the point where the lug is soldered to the segment of ths com- 
mutator. 

To remedy the fault, the brushes should be examined to 
see if any periodical vibration takes place. If such is the 
case, the cause should be removed, and the flat carefully filed 
or turned out, and the brushes readjusted. If it is due to a 
difference in the composition of the metal of which the seg 
ment is made, the flat will exist as long as the particular seg- 
ment is in use, and will need to be periodically turned out if 
a new segment is not fitted into the commutator. Now that 
the construction of commutators has been improved, how- 
ever, by the use of hard-drawn copper or phosphor-bronze 
segments, this fault is rarely due to this last-mentioned 



NEW CATECHISM OF ELECTRICITY. 



245 



Fig. 112. 




THE BOSTON MACHINE. 



Fig. 113. 




THE PHILADELPHIA MACHINE. 



246 NEW CATECHISM OF ELECTRICITY. 



FAULTS IN ARMATURES. 

cause. It is more frequently due to bad soldering, or jointing 
of the conductors to the lugs, or of the lugs to the segments. 
In all cases of flats, if the disconnection in the armature circuit 
is not complete, and cannot be readily located, the effect of 
re-soldering or sweating the ends of the coils into the lugs 
should be tried. Flats may also frequently be cured by drilling 
and tapping a small hole in the junction between the lug and 
the segment, and inserting a small screw, or bit of screwed 
copper or brass wire, afterwards filing down level with the 
surface of the commutator. 

(5.) Short Circuits in Commutator. — These are of frequent 
occurrence, and result in heating of the armature and spark- 
ing at the brushes. They are caused either by metallic dust 
or particles lodging in the insulation between the segments, 
or by the deterioration of the commutator insulation. 

To remedy, the insulation between the segments should be 
carefully examined, and any metallic dust, filings, or burrs 
cleaned or scraped out. When the commutator is insulated 
with asbestos or pasteboard (as is oftentimes the case in dyna- 
mos of continental make), short circuits very frequently occur 
through the insulation absorbing moisture or oil, which is 
subsequently carbonized by the sparking at the brushes. In 
faults of this description the only remedy is to expel all 
moisture from the commutator insulation by means of heat, 
and scrape out all metallic dust which may be imbedded in 
the surface of the insulation. If this does not effect a cure, 
it will be necessary to dig out the insulation, as "far as possi- 
ble, with a sharp tool, and drive in new insulation ; oil 



NEW CATECHISM OF ELECTRICITY. ^47 

FAULTS IN ARMATURES. 

should not be used on commutators insulated with these ma- 
terials, but only asbestos dust or French chalk. 

(6.) Rough and Uneven Surface of Commutator. — This 
fault is due to bad adjustment of brushes, bad construction of 
commutator, and to neglect generally. If allowed to con- 
tinue, it results in heavy sparking at the brushes, and the 
eventual destruction of the commutator. The fault may be 
remedied by filing or turning up the commutator in the man- 
ner explained previously. 

(7.) Segments Loose or Knocked in. — When the segments 
are loose, it is an indication that the clamping ring or cone 
has worked loose. This should therefore be tightened up, 
and the commutator turned up. When the commutator re- 
ceives an accidental blow, one or more of the segments is 
invariably forced below the level of the others. In this con- 
dition the commutator is practically useless. To remedy, 
two courses are open : the commutator surface may be 
turned down to the level of the knocked-in segment, or the 
latter may be pulled out again to its former level, this latter 
being the preferable method, if it can possibly be effected. 
To pull out the segment, a hand vice is firmly clamped to the 
lug, or a loop of copper wire is passed round the conductor 
where it joins on to the commutator. A bar of iron to act as 
a lever is supported on a fulcrum over the commutator, and 
one end of the bar is passed through the loop or vice. On 
pressure being applied to the other end, the knocked in seg- 
ment can generally be brought up to its former level. The 
commutator can then be filed up with a dead smooth file. 



248 



NEW CATECHISM OF ELECTRICITY. 



METHOD OF MEASUREMENT. 



As most installations are in practice provided with an 
ammeter and voltmeter, the current and pressure may be 
measured with facility. The instruments are arranged as 
represented in Fig. 114. D is a dynamo or other generator, 



Fig. 114. 




© <D © <b 



the positive and negative terminals of which are connected to 
the two mains M M between which the lamps 1/ L are con- 
nected in parallel. To indicate the amount of current flowing 
in the circuit, an ammeter A is inserted in "series " in one of 
the mains and with the lamps, and therefore the whole of the 
current passing to the lamps passes through the ammeter, and 
is measured by the latter. A voltmeter V is connected across 
the two main leads, or in shunt with the dynamo, and meas- 



NEW CATECHISM OF ELECTRICITY. 249 

METHOD OF MEASUREMENT. 

ures the difference of potential between the two mains in volts. 
By taking simultaneous readings of the voltmeter and ammeter 
the energy being expended in the circuit can be ascertained by 
equation (i). For example, suppose the voltmeter to indicate 
100 volts, and the ammeter ioo amperes, then by equation (i) 
KC=W. 100X100= 10,000 watts are being expended in the 
oircuit. The output of dynamos is usually expressed in watts, 
as this indicates the actual electrical power given by the 
machine, irrespective of the strength of the current, or its 
pressure, which may be varied to any extent so long as their 
product remains constant. For example, a machine designed 
for an output of 100,000 watts may be arranged to give 1,000 
amperes at a pressure of 100 volts, or 10,000 amperes at 10 
volts pressure, or 100 amperes at 1,000 voits pressure. The 
power required to drive the machine under these varying 
pressures and currents will remain the same, since their pro- 
duct remains constant. The power required to work incan- 
descent and arc lamps and other electrical appliances is also 
expressed in watts. 

To measure the rate at which work is done by a current in 
a wire, or in a lamp, or other thing supplied with electric 
power, we must measure both the amperes of current that are 
running through it, and the volts of electro-motive force that 
are actually applied at that part of the circuit, and having 
found the two numbers we must multiply them together. 

For just as engineers express power mechanically as the 
number of * c foot-pounds ' ' expended in a given time, s6 the 
electrician expresses electric power as the number of " volt- 



250 



NEW CATECHISM OF ELECTRICITY. 



Frc. 11*. 




Erie (penna.) machine. 



NEW CATECHISM OF ELECTRICITY. £5! 

METHOD OF MEASUREMENT. 

amperes." The more convenient name of "one watt" is 
given to the unit of electric power. Calculation shows that 
one "watt" or "volt-ampere" is equal to one seven-hundred- 
and-forty- sixth part of a horse-power. 



Note.— A good dynamo will convert over 90 per cent, of the mechani- 
cal power supplied to it into electric power. Similarly a good motor will 
convert over 90 per cent, of the electric power supplied to it into mechani- 
cal power. Both mechanical power and electric power may be expressed 
in terms of the same units, either in horse-power, or in watts, or in kilo- 
watts. 

Approximate calculations of the horse-power required for a dynamo 
of any prescribed output are readily made. Multiplying the number of 
amperes of current which the dynamo is to yield, by the number of volts 
of pressure at which the current is supplied, gives the output in watts. 
Dividing by 746 gives the corresponding electric horse-power, which will 
be about 90 per cent, of the mechanical horse-power to be supplied to the 
shaft of the dynamo. 

Kx. A dynamo is required to furnish 300 amperes at a pressure of 105 
volts. Output is 31,500 watts = 42.2 horse-power (electrical). Therefore 
allow 46.9, or say 50 (mechanical) horse-power. 

In the converse way we may calculate the requisite supply of electric 
power to a motor. 

Ex. A motor is required to give an actual output of 5 horse-power. 
Multiplying by 746, we find it must give out 3,730 watts as mechanical 
power ; which will be about 90 per cent, of the electrical power supplied 
to it. This will therefore need to be about 4,144 watts. If the supply is 
from mains that are at a pressure of 200 volts, the current required will 
consequently be a little over 21 amperes. 

As an example of calculation of electric power the following may be 
taken. It was required to ascertain the power expended in maintaining 
a certain arc lamp. The voltmeter showed an electric pressure of 57 volts 
between the terminals of the lamp, and the amperemeter showed a cur- 
rent of 10.5 amperes running through it. The product is 598.5 watts. 
Dividing by 746 to bring to horse-power, we get 0.80, or eight-tenths of a 
horse-power. 



2£2 NEW CATECHISM OF ELECTRICITY. 



DESIGNING A DYNAMO 



As in all designing of machines, so with the designing of 
dynamos, experience is the ultimate guide. To design a 
machine which, when driven at a prescribed speed, shall yield 
any desired number of an_peres of current at any given 
voltage, is a very simple matter to an engineer who has 
already had experiance in designing dynamos of the same 
general type, but of different output. To one who has 
designed two-pole continuous current machines for incandes- 
cent lighting it is a simple matter to design another machine 
of the same sort. But it would be to him by no means so 
easy from his experience only to pass to designing machines 
of a multipolar type, or to design alternate-current machines. 

But to begin anew to design a dynamo without this kind 
of practical basis is a different matter. The first stage in 
understanding this is to examine carfully the design of some 
well-established machines, and to see how the dimensions of 
their several parts are adapted to their functions. It will 
then be an easier matter to work out any case for a fresh type 
of machine. 

Calculations are needed to ascertain the proper sizes of the 
parts. Some of these calculations are purely electrical, others 



NEW CATECHISM OF ELECTRICITY. 253 

DESIGNING A DYNAMO. 

magnetic, others mechanical, and some are of a wholly 
empirical nature founded on experience. 

It is known, for example, that the number of watts of out- 
put of a dynamo of given form, and a given speed, is approxi- 
mately proportioned to its weight. For example : given a 
dynamo which at 720 revolutions per minute yields (without 
sparking or overheating) 200 amperes at 105 volts, it is known 
that using the same iron carcase, and rewinding the machine 
with new coils equal in weight to those previously used, the 
machine may be made to give (at same speed as before) 
300 amperes at 70 volts, or 250 amperes at 84 volts, or 30 
amperes at 700 volts — the product in each of these cases being 
21,000 watts. A machine for double the output would have 
double the weight of iron and double the weight of copper, 
approximately, if of the same type. 

Also, since the voltage is proportional to speed, if a new 
dynamo had to be designed to give the same output at a 
speed of 480 instead of 720 revolutions per minute, a carcase 
about \ x / 2 times as heavy would be required. 

Fig. 116. 




254 



NEW CATECHISM OF ELECTRICITY. 



Fig. 117. 




PARTS OF 
EDISON BIPOLAR GENERATOR. 



NEW CATECHISM OF ELECTRICITY. 



255 



LIST OF PARTS OF EDISON BIPOLAR GENERATORS. 



1. Rails. 

2. Adj listing Rail-Bolts. 

3. Bed-Plate. 

4. Zinc Bases for Fields. 

5. Pole Pieces. 

6. Conductor Rods. 

7. Field Coils and Cores. 

8. Lower Screws, field cores to pole 

pieces. 

9. Bolts for attaching keeper to pole 

pieces. 

10. Washer for same. 

11. Keeper. 



1 2. Backboard and field coil terminal 

blocks. 

13. Bolts for same. 

14. Head-board. 

15. Bolts for same. 

16. Rib Side- Plate. 

17. Panel Side-Plate for Name-plate. 

18. Pillow Block Base, Commutator 

End. 

19. Pillow Block Complete, Pulley- 

End. 

20. Drirj Cock for self-oiling bear- 

ings. 



Fig. 118. 




21. Bearing Sleeve for self-oiling 

bearings. 

22. Rings for self-oiling bearings. 

23. Cap for Pillow Block. Commuta- 

tor end. 

24. Armature Complete. 

25. Commutator Complete. 

26. Comt. Cap for ends of Armature 

coils. 

27. Armature Pulley. 

28. Brush Yoke. 

29. Bolt for same. 

30. Spring Washer for adjusting 

tension. 



39- 



Thumb Screw for Yoke. 

Brush-holder Complete. 

Insulating Blocks for Bruhh- 
Holder. 

Insulating Washer for Brush- 
Holder. 

Brushes. 

Foot-Boards. 

Brush-Holder Cables. 

Wire Screen for protecting Arm 
ature. 

Brush Filing Jig. 



40. Generator Wrench, 



256 



NEW CATECHISM OF ELECTRICITY. 



DISTORTION OF MAGNETIC FIELD IN THE 
DYNAMO. 



As soon as a dynamo commences to supply current to a cir- 
cuit, a number of reactions between the armature and mag- 
netic field immediately takes place. The chiefest of these 



Fig. 119. 
v 







reactions is the distortion of the magnetic field, and consequent 
shifting of the neutral points. This distortion of the magnetic 
field is directly due to the fact that the armature, when 



NEW CATECHISM OF ELECTRICITY. 257 

DISTORTION OF MAGNETIC FIELD. 

working, becomes itself an electro magnet, the poles of which 
exert an attracting or repelling force upon the magnetic field. 
The nature of this armature magnetism will be understood by 
reference to Fig. 119. It will be seen that the currents generated 
in the windings on each side of the armature, by its motion 
in the magnetic field, are flowing from the top to the bottom 
of the ring. On applying the rule given on page 81, it will 
be found that these currents tend to produce north and south 
poles on each half of the core at the points where the current 
enters and leaves the armature. There will thus be two north 
poles at the top of the ring, and two south poles at the bottom ; 
but as these poles are adjacent to one another, the external 
effect will be equivalent to a single north and south pole situ- 
ated at the top and bottom of the ring. The resulant effect 
of these two armature poles upon the magnetic field is to 
twist the line of force round into an oblique direction as shown 
in Fig. 120. Since in order to secure sparkless collection of 
the current and to obtain the greatest difference of potential 
between the brushes, it is necessary to place these latter at 
points situated at right angles to the direction of the lines of 
force in the armature, the twisting of the lines necessarily 
involves the shifting of the brushes round the commutator in 
the direction of rotation, otherwise the armature coils will be 
short circuited by the brushes while actively cutting the lines 
of force, and considerable sparking at the brushes will result. 






258 



NEW CATECHISM OF ELECTRICITY. 



EDDY CURRENTS. 



Another very important action which occurs when the 
dynamo is working is the production of eddy currents in differ- 
ent parts of the machine. 

Fig. 120. 




This term is applied to the currents which are always pro- 
duced when a solid metallic mass is rotated in a magnetic 
field, or is subjected to the action of a magnetic field which is, 
undergoing change in its intensity or strength, for the reason 
that the currents generated always tend to flow in more or 
less circular paths. When produced in large solid metallic 
masses, the strength to which these eddy currents attain is 
frequently very considerable, owing to the low electrical re- 
sistance of the masses in which they flow ; and, in addition to 
consuming a large amount of energy, they frequently occa- 
sion a large and dangerous rise in the temperature. The 



NEW CATECHISM OF ELECTRICITY. 259 



EDDY CURRENTS, 
cores of armatures being made of iron, are, unless suitably 
constructed, subject to the detrimental influence of these 
eddy currents, as is also the case with the conductors wound 
upon the core if these are of large cross-sectional area. To 
entirely prevent the generation of these eddy currents is im- 
possible ; they can, however, be prevented attaining any 
considerable strength, by suitably interposing resistance in 
their path. With this object, the cores and conductors of 
armatures are laminated, or subdivided into a number of 
small parts, each of which is electrically insulated from the 
other by some insulating material. 



COUPLING UP FIELD MAGNET COILS. 



In coupling up the exciting coils of dynamo field magnets, 
the primary essential is to so arrange the connections of the 
coils that the magnetizing current flowing through them pro- 
duces the requisite polarity in the respective pole'pieces. In 
those field magnets provided wirh a single coil only (as in 
'Fig- 76) > no mistake can obviously be made ; when two or 
more coils are used, however, it is possible to so arrange the 
connections that poles are produced in the yokes or other por- 
tions of salient pole field magnets ; or in case of consequent 
pole field magnets, the connections may be so arranged that 
the coils neutralize each other, and no external field whatever 
is produced in the manner in which the coils of the various 
types of salient and consequent pole field magnets are coupled. 



26o NEW CATECHISM OF ELECTRICITY. 



DISEASES OF DYNAMOS. 



Taken as a whole, an electric machine is remarkably dur- 
able, and the cost of maintenance very small. There are 
only three parts that can really wear away — these are the two 
journals and the commutator. The shafts in nearly all 
machines are made of steel, and in some are even hardened 
and ground. Therefore the wear in the journals takes place 
mostly on the boxes, and these, being interchangeable, can be 
replaced in a few minutes and at small expense when worn 
out. The commutators, if they run without sparking, should 
last several years. k 

As there are virtually only three parts that really wear out, 
it might be supposed that the renewal of these parts would be 
all that would be required to keep the machine in perfect 
running order. But experience shows that such is not the 
case. 

At least four-fifths of the mishaps and break-downs that 
occur with dynamos arise from causes more strictly within the 
province of the engineer than in that of the electrician. On 
the other hand, many of the mechanical faults that develop 
themselves in the machine might have been avoided had the 
engineer been possessed of a better knowledge of the electric 
and magnetic conditions which obtain in the running of the 
machine. 



NEW CATECHISM OF ELECTRICITY. 26l 

DISEASES OF DYNAMOS. 

In the practical operation of dynamos and motors as well 
the following is a list which covers nearly everything which 
should be first considered as faults or diseases : 

First. — Failure to excite or generate, i. e. y when the ma- 
chine is running the current does not flow. 

Second. — Heating .of armature, field magnets, commutator 
or brushes, or heating of the bearings. 

Third. — Sparking at commutator. 

Fourth. — Too high or too low speed. 

Fifth. — Excessive noise or vibration. 

Sixth. — Variation of voltage. 

Each of these classes is distinct from the others, and when 
the "trouble" has been located, it will be seen that the 
remedying of one of the above list is nearly always all that is 
required — hence the importance of some study before apply- 
ing the cure. 

It is impossible to give complete direction for each occa- 
sion, but the lists will greatly aid the prompt and intelligent 
attendant. 



FAILURE TO EXCITE. 



The first point to be observed, if the machine fails to ex- 
cite, is the position of the brushes upon the commutator. If 
these are not on or near the neutral points, the whole of the 
E. M. F. of the armature will not be utilized, and will prob- 
ably be insufficient to excite the machine. If in doubt as to 



262 NEW CATECHISM OF ELECTRICITY. 

FAILURE TO EXCITE. 

the correct positions, the brushes should be rotated by means 
of the rocker into various points on the commutator, sufficient 
time, say five minutes, being given the machine to excite be- 
fore moving them into a new position. 

If the different points of contact of the connections of the 
machine are not kept thoroughly clean and free from oil, etc., 
it is probable that such resistance will be interposed in the 
path of the exciting current as to prevent the machine build- 
ing or exciting. Kach of the contacts should, therefore, be 
examined, and cleaned, and screwed up tight. The chief 
point to which attention should be given is the contact faces 
of the brushes arid surface of the commutator. These are 
very frequently covered with a slimy coating of oil and dirt, 
which is quite sufficient to prevent the machine exciting. 

In shunt and compound dynamos there is a certain critical 
speed below which they will not excite. If the normal speed 
of the machine is known, it can at once be seen whether the 
failure to excite arises from this cause, by measuring the speed 
of the armature with a speed indicator. In all cases it is advis- 
able, if the machine does not excite in the course of a few min- 
utes, to increase the speed to a certain extent. As soon as the 
voltage rises, the speed may be rednced to its regular amount. 

Insufficient residual magnetism is a fault, although not of 
frequent occurrence, and it is almost impossible for it to take 
place if the field magnets are of cast-iron. It always occurs 
when the dynamo is a new one, or when the field magnets 
have been taken apart for repairs, etc. It may be remedied 
by passing the current from a few storage cells, or another 



NEW CATECHISM OF ELECTRICITY. 263, 

FAILURE TO EXCITE. 

dynamo, for some time in the proper direction through the 
field coils. If a heavy current, such as is obtainable from a 
storage battery, is not available, and the machine is shunt or 
compound wound, a few Leclanche or dry cells will generally 
effect the purpose. 

Reversed magnetism in fields is a fault of infrequent 
occurrence. It may be caused by the proximity of other 
dynamos, but is generally due to reversed connections of the 
field coils. Under such conditions the field coils tend to pro- 
duce a polarity opposed to the magnetization to which they 
owe their current, and, therefore, the machine will refuse to 
excite until the field connections are reversed, or a current is 
sent from another dynamo or a battery through the field coils 
in a direction to produce the correct polarity in the pole 
pieces. 

A dynamo may refuse to excite through some portion of 
its windings or connections being short circuited, for the 
reason that the field magnets are deprived of the necessary 
current required for building the machine. Short circuits 
most frequently occur in terminals, brush-holders, commu- 
tator, armature coils, field coils. 

The terminals of the various circuits of the machine are 
liable to be short circuited, either through metallic dust 
bridging across the insulation, or through the terminals mak- 
ing direct contact with the frame of the machine. The various 
terminals should be examined, and if the fault cannot be 
located by inspection, they should each be disconnected from 
their circuits and tested with a battery and galvanometer. 



264 NEW CATECHISM OF ELECTRICITY. 



EXCESSIVE HEATING OF DYNAMOS 



The excessive heating of the constituent parts of a dynamo 
is probably the most common and at the same time the most 
annoying fault which arises in the working of the dynamo. 
It may be due to various causes, electrical or mechanical ; 
and may occur in any one or more of the component parts of 
the dynamo : 

(1.) Connections. 

(2.) Armature, commutator, brushes. 

(3.) Field magnets. 

(4.) Bearings. 

It may be detected by applying the hand to the different 
portions of the machine if low tension, or a thermometer if 
high tension, and also by a smell of over-heated insulation 
and paint or varnish. When this last indication is felt, it is 
advisable to stop the machine at once, otherwise the insula- 
tion is liable to be destroyed. 

1. Heating of Connections. — This may proceed from 
either or both of the following causes : 

(a) Excessive Current. — The terminals and connections 
will be excessively heated if a larger current passes through 
them than they are designed to carry. This nearly always 



NEW CATECHISM OF ELECTRICITY. 265 

EXCESSIVE HEATING OF DYNAMOS. 

proceeds from an overload of the dynamo, and if this is 
rectified as directed in (4) "Overload of Dynamo," the heat- 
ing will disappear. 

(b) Bad Contacts. — If the contacts of the different con- 
nections of the dynamo are not kept thoroughly clean and 
free from all grit, oil, etc., and the connections themselves 
are not tightly screwed up, great heating will result, and they 
may even be unsoldered. 

2. Heating of Armature, Commutator and Brushes. — 
When excessive heating occurs in these portions of the dy- 
namo, it may proceed from any of the following causes : 
(a) Excessive current ; (b) Heated bearings ; (c) Short cir- 
cuits in armature or commutator ; (d). Moisture in armature 
coils ; (e) Disconnections in armature coils ; (f) Eddy cur- 
rents in armature core or conductors. 

(a) Excessive Current. — When the dynamo is overloaded 
the temperature of the armature will rise to a dangerous ex- 
tent, depending upon the degree the safe capacity of the 
machine is exceeded, and heavy sparking of the brushes will 
also result. If the overload is not removed as directed in 
(4) "Overload of Dynamo," the insulation of the armature 
may be destroyed. 

(b) Heated Bearings. — If the bearings are heated, the 
heat may be conducted along the armature shaft and core, 
thus giving rise to excessive heating of the armature. 

(c) Short Circuits in Armature or Commutator. — This 
fault results in sparking at the brushes, and in excessive 



266 NeW catechism of electricity. 

EXCESSIVE HEATING OF DYNAMOS. 

heating of one or the whole of the armature coils, and even 
in the burning up of the latter if a bad case. When the 
armature is overheated, and the defect does not proceed from 
an overload or the causes mentioned below, the dynamo 
should be immediately stopped and tested for this fault. 

(d) Moisture in Armature Coils. — The effect of this fault 
being to practically short circuit the armature, a heating of 
the latter results. In bad cases steam or vapor is given off. 

(e) Disconnections in Armature Coils. — This fault results 
in local heating of the armature, for the reason that resist- 
ance is interposed in the path of the current at the fracture. 
It always results in sparking at the brushes, and the heating 
being confined to the neighborhood of the disconnection. 

(/) Eddy Currents in Armature Core or Conductors — 
When the construction of the armature core and conductors 
does not fulfil the necessary conditions required for the pre- 
vention of Eddy currents, such as the laminations not being 
sufficiently insulated or numerous enough, a great heating of 
the whole of the armature results, which may even extend to 
the bearings. There is no remedy for this defect other than 
the purchase of a new armature, or the entire reconstruction 
of the old. The fault may be detected by exciting the field 
magnets and running the machine on open circuit, with the 
brushes raised off the commutator for some time, when the 
armature will be found to be excessively heated. 

3. Heating of Field Magnets. — When the field magnets 
are found to be excessively heated, they should be tested for 



NEW CATECHISM OF ELECTRICITY. 267 

EXCESSIVE HEATING OF DYNAMOS. 

the following faults in the order given : (a) Excessiv e excit- 
ing current ; (b) Moisture in field coils ; (c) Short circuits in 
field coils ; (d) Kddy currents in pole pieces. 

(a) Excessive Exciting Current. — When the excessive 
heating arises from this cause, all the exciting coils will be 
heated equally. It may be due to excessive voltage, in the 
case of shunt dynamos ; or to an overload in the case of 
compound and series dynamos. In either case it may be 
remedied by reducing the voltage or overload as directed in 
(4) " Overload of Dynamo." If due to the coils being incor- 
rectly coupled up, i. e., coupled up in parallel in place of 
series, it will be necessary to rectify the connections or insert 
a resistance in series. 

(b) Moisture of Field Coils. — As in the armature, the 
presence of damp or moisture in the field coils tends to de- 
crease the insulation resistance, thus in effect producing a 
short circuit with its- attendant heating. The fault may 
easily be detected by applying the hand to the field coils, 
when they will be found to be damp, and in addition steam 
or vapor will be given off where the machine is working 
The fault may be remedied by drying and varnishing the 
coils. 

(c) Short Circuits in Field Coils. — This fault is character- 
ized by an unequal heating of the field coils. If the coils are 
connected in series, the faulty coil will be heated to a less ex- 
tent than the perfect coils. If, on the other hand, they are 
connected in parallel, the faulty coil will be heated to a 



2 63 NEW CATECHISM OF ELECTRICITY. 



Fig. 121. 




BARRIER MACHINE (N. Y.) 



NEW CATECHISM OF ELECTRICITY. 25a. 

EXCESSIVE HEATING OF DYNAMOS. 

greater extent than the perfect coils. The faulty coil can 
thus be easily located by this indication. 

(d) Eddy Currents in Pole Pieces. — This fault may be 
due to defective design or construction of the armature. 
Toothed core armatures are particularly liable to cause this 
fault, if the teeth and air gap are not properly proportioned. 
The defect may also be occasioned by variation in the 
strength of the exciting current. 

If due to this latter cause, it will be accompanied by 
sparking at the brushes. If a shunt dynamo, insert an am- 
meter into the shunt circuit, and note if the deflection is 
steady. If this is not the case, the variation in the current 
most probably proceeds from imperfect contacts thrown into 
vibration. 

4. Heating of Bearings. — The heating of the bearings is 
of frequent occurrence in the working of dynamos, and is 
probably the most troublesome fault to which they are sub- 
ject, as its origin is, as a rule, obscure. When the bearings 
heat excessively, so that the heat cannot be borne by the 
naked hand, and such simple remedies as the supply of fresh 
lubricant, or slacking back the caps of the bearings or the 
belt fails to remedy the trouble, the dynamo should be 
stopped, as it indicates something radically wrong. 

The use of water on heated bearings has been recom- 
mended, but its use is questionable. No doubt it cools the 
bearings for the time being, and allows of the machine being 
run for a short time longer ; but when the bearings are in 



270 NEW CATECHISM OF ELECTRICITY. 

EXCESSIVE HEATING OF DYNAMOS. 

such condition as to need the application of water, probably 
as much damage is done to the journals and liners, through 
scoring, etc., as more than counterbalances any slight gain 
secured through running the machine while the bearings are 
heated. Removing the lubricators, and flooding the bear- 
ings and journals with ordinary or castor oil, tends to re- 
duce the heating ; or the effect of sulphur mixed with oil, 
and applied direct to the bearings, after removing the lubri- 
cators, should be tried. If these remedies fail, the machine 
should be stopped, and the cause of the heating ascertained. 
As a rule, heating of the bearings is due to — (a) Defective 
lubrication or bad oil; (b) Journals too tight; (c) Belt too 
tight ; (d) Dirt, grit, etc., in bearings ; (e) Rough or badly 
fitted journals or bearings ; (/) Bent or badly turned shaft ; 
(g) End pressure of shaft against bearings ; (k) Armature 
incorrectly placed in armatnre chamber ; (i) Badly propor- 
tioned bearings ; (j ) Bearings out of line ; (k) Conduction of 
heat from armature. 

(a) Defective Lubrication or Bad Oil. — When the bearings 
heat up, first examine the lubricators to see that they are 
full, and that they feed the lubricant properly, and that none 
of the feed or waste oil passages are clogged. It is advisable 
to pass the end of a piece of wire down each of the passages 
occasionally to clear them. The quality of the oil supplied 
to the lubricators should be of the best mineral oil, perfectly 
clean and free from grit. It is advisable not to use the waste 
oil for the dynamo again ; but if used, see that it is well 
filtered. In some instances, hot bearings, due to defective 



NEW CATECHISM OF ELECTRICITY. 271 

EXCESSIVE HEATING OF DYNAMOS. 

lubrication, have been remedied by cutting grooves ob* 
liquely in the face of the liners for the better circulation of 
the Oil. 

(b) Journals too tight. — If the caps of the bearings are 
screwed up too tight, the hearings are bound to heat up. As 
the armature spindle or shaft is not subjected to any recip- 
rocal stresses, it is only needful to have the caps of the bear- 
ings screwed up hand tight. If the top brass does not bear 
upon the bottom brass, it may be necessary to scrape open 
the bearing a little, or insert a liner between the top 
and bottom brasses, until the spindle revolves freely by 
hand. 

(c) Belt too tight. — Heating of the bearings may be due 
to too great a tension of the belt, caused either by an over- 
load of the dynamo, or through too narrow a belt being used 
for the work, thus necessitating the dynamo being screwed 
up tightly upon the slides. When this is the case, the bear- 
ing next the pulley will be heated more than the other. 
The remedy is to reduce the load upon the dynamo, as 
directed in B (4) " Overload of Dynamo," or get a broader belt 
and pulley and run with some slack on the belt. 

(d) Dirt y Grit, Etc., in Bearings. — The presence of the 
smallest quantity of grit in the lubricant or bearings will re- 
sult in great heating of the latter, and in scoring of the shaft 
and liners, if not removed quickly. The machine should be 
stopped if possible, and the caps of the bearings taken off 
and the armature taken out of the bearings, and the latter 
carefully cleaned and scraped up smooth. 



272 NEW CATECHISM OF ELECTRICITY. 

EXCESSIVE HEATING OF DYNAMOS. 

If the journals are scored to any extent, it will be neces- 
sary to put the armature in the lathe and carefully file them 
up with a dead-smooth file before replacing. If the machine 
cannot be stopped at once, the lubricators should be made to 
feed very fast, or removed entirely, and the bearings continu- 
ously flooded with oil by means of an oil can until the ma- 
chine can be conveniently stopped. 

(e) Rough or Badly Fitted Journals or Bearings. — To 
ensure cool running, the journals should be perfectly smooth 
and true, and bear upon the surface of the liners throughout 
their entire length and width. 

To ascertain if this is the case, the caps of the bearings 
should be removed, and a little i ' marking, ' ' composed of 
red lead or other coloring matter and ordinary oil, rubbed 
upon the journals. The caps should then be replaced, and 
the nuts screwed up to working pressure, and the armature 
rotated a few times. The caps- should then be again re- 
moved, and the armature taken out, and the bearings exam- 
ined. If the journals are bearing all over the surface of the 
liners, the fact will be indicated by the marking being dis- 
tributed equally all over. If this is not the case, the project- 
ing portions of the liners, as indicated by the marking, 
should be carefully scraped up and the armature put back 
again, and the bearings tested from time to time until the 
journals bear all over as indicated by the marking being 
equally distributed all over the surface of the liners. 

{/} Bent or Badly Turned Shaft. — A bent shaft can be 
detected by rotating it with the hand. If bent, it will 



NEW CATECHISM OF ELECTRICITY. 273 

EXCESSIVE HEATING OF DYNAMOS. 

"bind " at some portion of the revolution. If only slightly 
bent, the shaft should be placed in the lathe and carefully 
sprung back approximately straight, a light cut being taken 
off the journals to finally true it. The bearings will then 
need to be carefully refitted, as directed above. If badly 
bent, the only remedy is a new one. A badly turned shaft 
may be detected by means of the calipers and marking, as 
described above. If not truly circular, the marking will be 
unequally distributed over the journals. 

(g) End Pressure of Shaft against Bearings. — This may 
be caused either by the shaft not being truly level, or 
through the belt not being truly aligned, or through there 
being no "end play." In the former case, carefully test the 
journals with a spirit-level, and pack up the dynamo or slide 
rails until perfectly level. If the belt does not run true 
upon the pulleys, it will be necessary to align the machine 
by moving it upon the sliding bedplate until the centre of 
the belt runs upon the centre of the pulley. If no end play 
exists, the shaft will be bound between the collars and the 
bearings, and the defect will be visible to the eye. 

The correct amount of end play required varies with the 
size of the dynamo and method of driving adopted. In di- 
rect driven dynamos, it the collars of the journals are clear 
of the ends of the bearings, no end play is needed. In belt- 
driven dynamos, it is necessary to have from one-eighth to 
three-eighths of an inch of end play. In all cases it may be 
ascertained if the correct amount of end play is present by 
running the dynamo and observing, when slight pressure is 



•2 74 NEW CATECHISM OF ELECTRICITY. 

EXCESSIVE HEATING OF DYNAMOS. 

applied to one end of the shaft, if any end motion is pro- 
duced. If no end motion is obtained, or a strong pressure is 
needed to obtain the latter, the face of the collar or end of 
the bearing against which the shaft bears should be filed or 
turned down, until the correct amount is obtained, when the 
machine is running. 

(h) Armature Incorrectly Placed in Armature Chamber. — 
When the field magnet of a dynamo is Excited, it has a 
tendency to attract the iron core of the armature. The di- 
rection and intensity of the attractive force varies with the 
type of field magnet and the position of the armature core in 
the armature chamber or bore. In vertical horse-shoe mag- 
nets of the over-type form (Fig. 77), if the armature is placed 
exactly in the centre of the armature chamber, there is a 
tendency for the armature to be attracted downwards, the in- 
tensity of the attraction varying with the strength of the field 
magnets. In large dynamos this attractive force may even 
amount to some thousands of pounds, and therefore, if the 
armature core is not placed in the armature bore in such 
position as to balance or nullify the attractive force, the bear- 
ings are liable to heat up through the excessive pressure 
brought to bear upon them. To counterbalance the attractive 
force, it is necessary in such dynamos to place the armature 
slightly above the centre of the armature chamber. In field 
magnets of the undertype form (Fig. 78), the attraction is in 
an upward direction, and therefore, as the weight of the core 
is lifted off the bearings, the latter are not so liable to heat 
up as in the case with the overtype form. In horizontal field 



NEW CATECHISM OF ELECTRICITY. 275 

EXCESSIVE HEATING OF DYNAMOS. 

2nagnets (Fig. 79, etc.), the attractive forces act in op- 
posite directions, and are therefore balanced ; and in such 
dynamos the armature core may be placed exactly in the cen- 
tae of the armature bore. A heating of the bearings is also 
liable to be occasioned through the attractive forces devel- 
oped by the centre of the armature core not being parallel 
with the centre of the armature chamber or bore, or through 
the core being nearer one pole piece thau the other. This 
may result from unequal wearing of the bearings, and there- 
fore the bearings should either be re-lined or the bolt holes of 
the bearings readjusted, or the bearings packed up until the 
armature is correctly centred. 

(i) Badly Proportioned Bearings, — The bearings will heat 
up if the wearing and bearing surfaces are not suitably pro- 
portioned for the work they have to perform. In such cases 
the bearings will heat at the first run of the machine. The 
only remedy is to put in new or larger bearings, or an ad- 
ditional one, if the shait is long enough, and arrangements 
can be made to admit of this being done. 

(J) Bearings out of Line. — This will be indicated by an 
unequal wear of the liners, and by the shaft binding or seizing. 
The remedy is to draw the bolt holes of the bearings until the 
bearings are correctly aligned with each other and with the 
armature bore. 

(k) Conduction of Heat from Armature. — The bearings are 
liable to heat up through the heat developed by an overload 
or short circuit of the armature, or the production of eddy 
currents in the core being conducted along the shaft, 



276 NEW CATECHISM OF ELECTRICITY. 



A CHAPTER OF "DON'TS." 



44 Don't " use waste on commutators. 

44 Don't" allow copper brushes to remain in contact with 
with commutators when the machine is at rest. 

*' Don't" get rattled at all the wires, cables and instru- 
ments at the switch board ; they are all useful and most of 
them absolutely necessary, and they are no more complicated 
than the piping about your plant with which you are now 
familiar. 

44 Don't " fail to remember when the belts are put on the 
machines they are designed to run like any other piece of 
mechanical apparatus of similar weight and speed. 

" Don't " forget to ask the man who is to set up new appa- 
ratus to give you printed or verbal directions for running it. 
If he is a ' ' square man ' ' he will cheerfully do this. 

44 Don't" fail to read the following, written by an engi- 
neer to a party seeking information. 



Note. — "You will find that there is an armature made to revolve 
between two or more * fields," and that as the latter become magnetized 
they have an attraction that tends to hold the armature from turning, but 
the belt knows a * good thing ' and 'pushes it along,' thus generating 
current which the winding carries to the commutator, where it is picked 
off by the brushes and passed along to the circuit. If your circuit is kept 
whole and the machine in good order, there is less need of trouble with 
it than with a buzz saw." 



NEW CATECHISM OF ELECTRICITY. 277 



FLASHING OR SPARKING. 



In all good dynamos there are certain positions upon the 
commutator for the brushes at which there will be absolutely 
no sparking so long as the commutator is kept clean and in 
good condition. In other dynamos, badly designed or con- 
structed, sparking occurs at all positions, no matter where 
the brushes are placed, and in such dynamos it is therefore 
impossible to prevent sparking at the brushes, no matter how 
well they are adjusted. 

When sparkiug occurs at the brushes of a good dynamo, 
two kinds may generally be distinguished by the practised 
eye, viz., those sparks due to bad adjustment of the brushes, 
generally of a bluish color, small when near the neutral points, 
and increasing in violence and brilliancy as the brushes recede 
from the correct positions upon the commutator ; and those 
due to dirty and neglected state of the commutator and 
brushes, these being distinguished by a reddish color and a 
spluttering or hissing. When due to this last-mentioned 
cause, it is impossible to suppress the sparking until the com- 
mutator and brushes have been cleaned up. In the former 
case, the sparks will disappear as soon as the brushes have 
been rotated into the neutral points. 

Another class of sparks appear when there is some more 
or less developed fault, such as a short circuit, or disconnection 



Fig. 122. 




EQUALIZER 
CONNECTION AT k 



W RHEOSTAT KJ 

FOUR POI,K MACHINE WITH CONNECTIONS. 



NEW CATECHISM OF ELECTRICITY. 279 

SPARKING AND FLASHING. 

in the armature or commutator. These are similar in character 
to those produced by bad adjustment of the brushes, but are 
distinguished from the latter by their not decreasing in 
violence as the brushes are rotated towards the neutral points. 
Having distinguished the classes of sparks which appear at 
the commutator of a dynamo, it remains to enumerate the 
causes tending to produce sparking. These are • 

(r.) Bad adjustment of brushes. 

(2.) Bad condition of brushes , 

(3 ) Bad condition of commutator. 

(4.) Overload of dynamo. 

(5.) lyoose connections, terminals, &c. 

(6.) Disconnections in armature circuit. 

(7.) Short circuits in armature circuit. 

(8. Short circuits or disconnections in field magnet circuit. 

1. Bad Adjustment of Brushes. — When sparking is pro- 
duced by bad adjustment of the brushes, it may be detected 
by rotating or shifting the rocker, by the indication that the 
sparking will vary with each movement. To obtain good 
adjustment of the brushes, it will be necessary to rock them 
gently backwards and forwards, until a position is found in 
which the sparking disappears. If a position cannot be found 
at which the sparking disappears, it is probable that the 
brushes are not placed diametrically apart upon the commu- 
tator, or that the neutral points are not situated in their true 
theoretical positions upon the commutator through some 
defect in the winding, &c. In this last- mentioned case, the 



28o NEW CATECHISM OF ELECTRICITY. 

SPARKING AND FLASHING. 

brushes may be strictly adjusted to their theoretically correct 
positions before starting the machine ; then, when the 
machine is started and the load put on, violent sparking 
occurs, which cannot be suppressed by shifting the rocker. 
If, however, one set of brushes only is observed, it will gener- 
ally be found that, at a certain position, the sparking at the 
set of brushes under observation ceases or is greatly reduced, 
while sparking still occurs at the other set. When this 
position is found, the rocker should be fixed by the clamping 
screw, and the brushes of the other set at which sparking is 
still occurring adjusted by drawing them back or pushing 
them forward in their holders until a position is found at 
which the sparking ceases, at which they should be fixed. 
Correct position of the brushes upon the commutator and the 
suppression of sparking is a matter of great importance, and 
any time spent in carefully adjusting will be amply repaid by 
the decreased attention and wear of the brushes and com- 
mutator. 

2. Bad Condition of Brushes — If the contact faces of the 
brushes are fused or covered with carbonized oil, dirt, &c, 
there will be bad contact between the brushes and commutator, 
and consequently great heating and sparking. Simple exam- 
ination will generally reveal whether this is the case. The 
remedy is to remove the brushes, one at a time if the machine 
is running, clean, file if necessary, trim, and readjust. If the 
brushes are exceedingly dirty, or saturated with oil, it will be 
necessary to clean them with turpentine, benzoline, or soda 
solution, before replacing. 



MEW CATECHISM OF ELECTRICITY. 28l 



SPARKING AND FLASHING. 

3. Bad Condition of Commutator. — If the surface of the 
commutator is rough, worn into grooves, or excentric, or had 
one or more segments loose, or set irregularly, the brushes 
will be thrown into vibration, and sparking will result. A 
simple examination of the commutator will readily detect 
these defects. The remedy for a rough commutator is to file 
it up while running with a dead-smooth file, afterwards polish- 
ing with finest emery cloth. If the commutator is untrue, 
the fact will be indicated when the machine is slowed down 
by a visible excentricity, or by holding the hand, or a stick in 
the case of high tension machines, against the surface while 
revolving, when any irregularity or excentricity will be ap- 
parent by the vibration or movement of the stick. The only 
remedy for an excentric commutator is to re-turn it as directed 
in the succeeding paragraph. Loose or high or low segments 
may be detected by the same means. 

The remedy for high segments is to tap them gently down 
with a small hammer or mallet, and if possible tighten up the 
clamping cones at the ends of the commutator. If it is im- 
possible to hammer the segments down, they should be filed 
down level with the rest of the commutator, or the commu- 
tator, re-turned. For low segments, the only remedy is to 
pull out the segments, or turn commutator down to their 
level. 

Re-turning Commutator. — In re-turning the commutator, 
the armature should first be carefully taken out of the armature 
chamber, avoiding knocks or blows of any kind. The whole 
of the windings should then in order to prevent any particles 



282 NEW CATECHISM OF ELECTRICITY. 

SPARKING AND FLASHING. 

of metal finding their way on to the surface of the armature 
at the time the commutator is being turned, be entirely 
wrapped in calico or canvas before the armature is put into 
the lathe. The armature should on no account be rolled upon 
the floor, or subjected to blows or knocks while being put 
into the lathe, the winding is liable to be ruined if this takes 
place. 

In re- turning the commntator, a sharp-pointed tool should 
be used with a very fine feed. A broad-nosed tool ought not 
to be used, as it is liable to burr over the segments. After 
turning, the commutator should be lightly filed up with a 
dead-smooth file, and finally polished with coarse and fine 
emery cloth. After the commutator has been turned and 
polished, the insulation between the segments should be 
lightly scraped with the tang of a small file to remove any 
particles or burrs of metal which may be likely to short circuit 
the commutator. The points where the armature wires are 
soldered to the lugs should also be carefully cleaned with a 
brush from any adherent copper dust, and should then receive 
a coat or two of shellac varnish. While the commutator is 
being turned, care should be taken that the setting marks for 
the adjustment of the brushes are not turned out if these are 
present. The same care should be used in putting the 
armature back into the armature chamber as was used in tak- 
ing it out, otherwise the insulation is liable to be seriously 
damaged. 

4. Overload of Dynamo. — It may happen through some 
cause or other that a greater output is taken from the machine 



i 



NEW CATECHISM OF ELECTRICITY. 283 

SPARKING AND FLASHING. 

than it can safely carry. When this is the case, the fact is 
indicated by excessive sparking at the brushes, great heating 
of the armature and other parts of the dynamo, and possibly 
by the slipping of the belt (if a belt-driven machine), result- 
ing in a noise. The causes most likely to produce overload 
are :— (a) Excessive voltage ; (b) Excessive current ; (c) Re- 
versal of polarity of dynamo ; (d) Short circuits or grounds in 
dynamo, or external circuits. 

{a) Excessive Voltage. — This will be indicated by the 
voltmeter, and by the brightness of the pilot lamp. It 
may be caused either by excessive excitaiton of the 
field magnates, or by excessive speed. In the former 
case, resistence should be introduced into the field 
circuit to diminish the current flowing therein if a shunt 
machine ; or if a series machine, a portion of the cur- 
rent should be shunted across the field coils by means of a 
resistance arranged in parallel with the series coils ; or the 
same effect may be produced in both cases by reducing the 
speed of the armature if this is possible. If due to excessive 
speed, which will be indicated by a speed indicator, the 
natural remedy is to reduce the speed of the motor driving 
the dynamo, or, if this is not possible, insert resistance into 
the dynamo circuit, as described above. 

(b) Excessive Current. — This will be indicated by the 
ammeter. If the dynamo is supplying arc lamps, the excessive 
current may possibly be caused by the bad feeding of the. 
lamps. If this is the case, the fact will be indicated by the 
oscillations of the ammeter needle; and by the unsteadiness 



284 NEW CATECHISM OF ELECTRICITY. 

SPARKING AND FLASHING. 

of the light. If incandescent lamps are in circuit, the fault 
may be caused by there being more lamps in circuit than the 
dynamo is designed to carry. Under such circumstances, 
another dynamo should be switched into circuit in parallel, 
or, if this is not possible, lamps should be switched off until 
the defect is remedied. When electro-motors are in circuit, 
sparking frequently results at the dynamo commutator, owing 
to the fluctuating load. In such cases the brushes should be 
adjusted to a position at which the least sparking occurs with 
the average load. 

(c) Reversal of Polarity of Dynamos. — When com 
pound or series wound dynamos are running in 
parallel, their polarity is occasionally reversed while 
stopping by the current from the machines at work. 
Under such conditions, when the machine is again 
started, the B. M. F. of one is added to that of another, or the 
machines are connected in series, so that a closed circuit is 
formed, and as a consequence an enormous current results. 
Before the machine can be again coupled in parallel, it will 
be necessary to send a current through the field coils in the 
reverse direction. 

(d) Short Circuits or Grounds in Dynamo or External 
Circuits.— A dynamo is liable to be overloaded through bad 
insulation of the dynamo or external circuits, resulting in a 
considerable leakage of current, in which case the ammeter 
will probably not indicate the fact. To ascertain if this is the 
case, connect a piece of insulated wire to one of the terminals 



NEW CATECHISM OF ELECTRICITY. 285 

SPARKING AND FLASHING. 

of the machine while running, and then make short momen- 
tary contacts with the ground through a water pipe, or frame 
of the dynamo, or other body in good connection with the 
earth. If a flash occurs, it proves that the insulation is 
defective somewhere. This test should be applied to each of 
the terminals in turn. The fault should next be located by 
taking the mains -to the external circuit out of the terminals 
of the machine, and again testing as before. If a flash again 
occurs, it proves that the defect exists in the dynamo, which 
should be stopped, and the terminals, etc., tested with a 
battery and galvanometer. It must be clearly understood 
that a fault of this description is just as likely to occur in the 
external circuit, and therefore, if after removing the mains 
from the terminals of the machine, and again testing, the 
flash disappears, it may be taken that the fault is in the ex- 
ternal circuit, which should be tested in a similar manner to 
the dynamo. 

(5.) Loose Connections, Terminals, c2fc. — When any of 
the connecting cables, terminal screws, etc. , securing the dif- 
ferent circuits are loose, sparking at the brushes, as a rule, 
results, for the reason that the vibration of the machine tends 
to continually alter the resistance of the various circuits to. 
which they are connected. When the connections are 
excessively loose, sparking also results at their points of con- 
tact, and by this indication the faulty connections may be 
readily detected. When this sparking at the contacts is 
absent, the whole of the connections should be carefully 
examined and tested. 



2 86 NEW CATECHISM OF ELECTFICITY. 



SPARKING AND FLASHING. 

(6. ) Disconnections in Armature Circuit.— 1£ there is a 
broken circuit in the armature, as sometimes happens, through 
a fracture of the armature connections, &c, there will be 
serious flashing or sparking at the brushes, which cannot be 
suppressed by adjusting the rocker. As a rule it results in the 
production of " flats" upon one or more bars of tl^e com- 
mutator. If it is impossible to stop the machine, the spark- 
ing may be much reduced by placing one of the brushes in 
each set a little in advance of the others, so as to bridge across 
the disconnection. If the machine is only provided with one 
brush on each side of the commutator, a bit of copper wire 
may be fixed in each holder, so as to project slightly in front 
of the brushes, and thus bridge over the broken circuit. 

(7.) Short Circuits in Armature Circuit.— -This fault is in- 
dicated by sparking at the commutator, and in bad cases by 
an excessive heating of the armature, dimming of the light, 
and slipping of the belt, and in the case of drum armatures 
by a sudden cessation of the current. 

(8. ) Short Circuits or Disconnections in Field Magnet Cir- 
^•/.—Either of these faults is liable to give rise to sparking 
at the commutator. If one of the coils is short circuited, the 
fact will be indicated by the faulty coil remaining cool while 
the perfect coil is overheated. The fault may arise through 
some of the connections to the coils making contact with the 
frame of the machine or each other. To ascertain this, ex- 
amine all the connections, and test with a battery and gal- 
vanometer. A total disconnection in one or more of the field 
coils may readily be detected by means of the battery and 



NEW CATECHISM OF ELECTRICITY. 287 

SPARKING AND FLASHING. 

galvanometer. A partial disconnection is not, however, so 
readily discovered, for the reason that the coil wires may be 
in sufficiently close contact to give a deflection of the gal- 
vanometer needle. The only methods of detecting this fault 
is by measuring the resistance of the coils with an Ohmeter 
or Wheatstone Bridge, or by placing an ammeter in circuit 
with each coil in turn, and comparing the amount of current 
flowing in each. If the short circuit is not accessible, the 
only way to remedy the fault is to rewind the coil, and the 
same applies to a disconnection if in the interior of the coil. 



288 



NEW CATECHISM OF ELECTRICITY. 



LIST OF PARTS. 



i. Armature (Ring Type). 

2. Left Hand Field. 

3. Right Hand Field. 

4. Pulley Leg. 

5. Commutator I,eg. 



6. Field Rods. 

7. Pulley. 

8. Automatic Regulator. 

9. Air Blast. 

10. Commutator. 



Fig. 123. 




ARC LIGHT GENERATOR. 



11. Brushes. 

12. Brush Holders. 

13. Pulley Bearing Cap. 

14. Oil Rings. 

15. Commutator Bearing Cap. 

16. Yokes. 



17. Regulator and Yoke Connection 

18. Vulcanite Connection Block. 

19. Binding Post an d Machine Con 

nections. . . 

20. Armature Short Circuitir 

Switch. 



NEW* CATECHISM OF ELECTRICITY. 



Fig. 124. 




THOMPSON-HOU$TON ARC-LIGHT GENERATOR (PARTS). 



29O NEW CATECHISM OF ELECTRICITY. 



VARIATION OF SPEED. 



This will be indicated by the dynamo failing to excite, or 
by a decrease of the voltage if the machine is working. The 
fault mav proceed from the undermentioned causes : — 

(1.) Reduced speed of driving engine; 

(2.) Overload of dynamo. 

(3.) Defective bearings. 

(4.) Short circuits in armature. 

(5.) Armature rubbing against pole pieces. 

(6.) Slack or dirty belt. 

1. Reduced Speed of Driving Engine. — It can readily be* 
ascertained whether the alteration in speed of the dynamo> 
proceeds from this cause by counting the revolutions of the 
engine with a speed counter. If at any time it is necessary to. 
run an engine driving a shunt or compound dynamo at ai 
lower speed than the normal, the voltage and output of the 
dynamo can generally be maintained at their ordinary value 
by coupling up the shunt coils in parallel, thus increasing the 
strength of the current flowing in the shunt circuit and the 
strength of the field correspondingly. Care should be taken, 
however, that the coils do not overheat with the increased 
current. 



NEW CATECHISM OF ELECTRICITY. 29I 

VARIATION OF SPEED. 

2. Overload of Dynamo. — When the reduction in speed 
proceeds from this cause, it is accompanied by excessive 
sparking at the brushes, and heating of the bearings and 
armature, and slipping of the belt. If the overload be re- 
moved as directed in Overload of Dynamo, the speed will 
again attain its normal value. 

3. Defective Bearings. — When due to this cause, the bear- 
ings will be excessively heated, and the shaft will " bind " or 
"seize," making a noise. It generally proceeds from de- 
fective lubrication, and may be remedied as directed in (4) 
Heating of Bearings. 

4. Short Circuits in Armature. — This practically amounts 
to an overload of the dynamo, and is accompanied by spark- 
ing at the brushes, heating of dynamo, and reduction of speed. 
The short circuit should be localized and repaired. 

5. Armature Rubbing Against Pole Pieces, — This will 
result in a diminution of speed if not remedied. 

6. Slack or Dirty Belt. — If the driving belt is not kept in 
good order, and free from oil, dirt, &c, a considerable amount 
of power will be lost in transmission. This will also be the 
case if the tension of the belt is not properly adjusted. If the 
motor driving the dynamo is a steam engine, turbine, or other 
steady running motor, the belt should in all cases be as tight 
as possible, consistent with the heating of the bearings. In 
the case of gas or oil engines, however, it will be necessary to 
have a certain amount of slack on the belt to allow of a little 
slip on the dynamo pulley, the amount varying with the 
irregularity of speed of the driving motor. 



292 NEW CATECHISM OF ELEC'i KICITT. 



VARIATION OF VOLTAGE. 



The pressure at the terminals of either shunt, series, or 
compound dynamos is liable to vary or fluctuate from various 
causes. In plain shunt or series wound dynamos a variation 
of pressure under a varying load follows as a consequence to 
the construction of the machine. A distinction, therefore, 
needs to be drawn between this natural variation of pressure 
and an abnormal fluctuation, which also affects compound 
dynamos, which may occur from time to time in the working 
of such machines. The causes tending to produce a fluctua- 
tion of voltage are : — 

(1.) Irregularities of speed. 

(2.) Bad joints in belt. 

(3.) Short circuits or disconnections in armature cir- 
cuit. 

(4.) Short circuits or disconnections in field magnet 
circuit. 

(5.) Incorrect connections. 

1. Irregulariiies of Speed. — Any cause tending to produce 
a variation in the speed of the dynamo is responsible for a 
variation of voltage. Steam engines, turbines, &c, give as a 
rule very little trouble in regard to irregularities of speed. In 
the case of gas and oil engines, however, an unsteadiness of 



NEW CATECHISM OF ELECTRICITY. 293 

VARIATION OF VOLTAGE. 

speed is always present, owing to their mode of action and 
construction. Before such motors can be used successfully in 
driving dynamos, this unsteadiness of speed needs to be re- 
duced and compensated as far as possible. With this object, 
such engines, when used for driving dynamos, are therefore 
fitted with extra heavy fly-wheels, and a fly-wheel is also 
fitted upon the armature spindle of the dynamo. In driving 
with such engines, the governors and valves are adjusted, if 
possible, to give an explosion at every revolution of the fly- 
wheel, and any little irregularity of speed is then compensated 
by varying the tension and slip of the belt on the dynamo 
pulley. 

2. Bad Joints in Belt. — If the belt is not jointed in a suit- 
able manner, it will cause a fluctuation of voltage, and a flick- 
ering of the light as the joint passes over the pulley. The 
belt should in all cases be soft and pliable, and made endless 
by a long spliced joint, or a butt joint with fasteners, or an 
endless link belt should be used. I^apped joints should on 
no account be used. 

3. Short Circuits or Disconnections in Armature Circuit. — 
When either of these faults is present, a periodical fluctuation 
of voltage will be set up, accompanied by sparking at the 
brushes. When this occurs- the machine should be stopped 
at once and the fault located and repaired. 

4. Short Circuits or Disconnections in Field Magnet Cir- 
cuit:— -Kither of these faults will give rise to a dimiuution or 
increase of voltage. To locate the faults, the entire field cir- 
cuit should be tested and examined. 



2Q4 NEW CATECHISM OF ELECTRICITY. 



VARIATION OF VOLTAGE. 

5. Incorrect Connections. — If on starting a machine for the 
first time, or after repairs, the voltage is either above or below 
its normal value, it is possible the variation may be the result 
of incorrect connections. The whole of the connections, in- 
cluding the armature, brushes, flexible leads, and field coil 
connections, should therefore be examined and verified. 



EXCESSIVE NOISE OR VIBRATION. 



The causes tending to produce excessive noise or vibration 
in a dynamo are : — 

(1.) Bad foundations. 

(2.) I/Oose screws, connections, &c. 

(3.) Belt joints. 

(4.) Bad adjustment of brushes. 

(5.) Knocking of shaft or pulley against bearings. 

(6.) Armature out of balance. 

(7. ) Armature knocking or rubbing against pole pieces. 

(8.) Straining of shaft couplings. 

These reasons for noise and vibration are self -explaining 
and the mere reading of them will suggest the appropriate 
remedy— but perhaps the more readily with the following 
paragraphs : 



NEW CATECHISM OF ELECTRICITY. 295 

EXCESSIVE NOISE. 

Excessive vibration can only be due to want of proper bal- 
ance in the armature. 

Vibration of another kind may nevertheless be disastrous 
to the dynamo, even in a well balanced machine, and this is 
caused by its not being firmly attached to a proper founda- 
tion. 

Continuous-current machines should run practically si- 
lently ; the belt will make far more noise than any part of 
the dynamo. 

Alternators do not usually run silently for the coils of all 
disk armatures churn the air between the poles. 

A case is recorded of a remarkable instance of an alternator, 
which emitted a sustained howling sound of piercing loud- 
ness. The cause was an accidental coincidence between the 
number of alternations and the natural vibration period of 
some of the solid iron parts. 



296 



NEW CATECHISM OF ELECTRICITY. 



WINDINGS OF ARMATURES. 



Fig. 125. 



Figs. 125 and 126 are simple diagrams showing the way in 
which wire is wound on drum and ring armatures, respec- 
tively. In both figures the coils are shown separated to more 

readily illustrate the prin- 
ciple. A little examina- 
tion of the figures will 
show that each section of 
the coil is connected to 
the next in order to it ; 
the whole of the windings 
constituting, therefore, a 
single closed coil. 




DRUM WINDING. 



Also the end of each section and the beginning of the next 
are both connected with a segment of the commutator. 

Fig. 126. 




RING WINDING. 



NEW CATECHISM OF ELECTRICITY. 297 

WINDING OF ARMATURES. 

Let it be remembered that in closed-coil armatures, whether 
of the "ring" or the "drum" type, there are usually as 
many segments to the commutator as there are sections or 
groups of coils in the circuit of the armature. In the case of 
open-coil armatures y the separate coils are not connected up 
together in series, and a special form of commutator is used 
instead of the usual arrangement of a large number of parallel 
bars. 

The principle of the ring or gramme armature is shown in 
Fig. 70. An iron ring capable of revolving upon an axis is 
arranged in the magnetic field between the poles N and S of 
an electro magnet. Upon this ring is wound a number of 
coils or loops of insulated copper wire, so as to cover the whole 
of the surface of the iron ring. The ends of each of the coils 
are connected to the ends of the adjacent coils, so that a con- 
tinuous closed spiral is formed all around the ring ; and, at 
the points where connection is made between the coils, con- 
nection is also made to strips of copper, which are insulated 
from each other and arranged around the axis of rotation 
into a circular commutator, as shown in the figure, against 
the two strips situated at opposite ends of a diameter press, 
two metallic brushes, Bi, B2, which, remaining stationary, 
serve to convey the current generated in the coils of the arma- 
ture to the external circuit K. 

The arrangement of the lines of force in the magnetic 
field between the two poles N and S, when the ring is inserted 
therein is shown in the dotted lines in the figure. 



2g8 NEW CATECHISM OF ELECTRICITY. 

WINDING OF ARMATURES. 

From this it will be seen that the lines of force issuing 
from the north pole pass by way of the armature core to the 
south pole of the magnet, one-half of the lines passing through 
the upper portion of the core and the other half passing 
through the lower portion of the core. Owing to this peculiar 
arrangement, a very intense magnetic field is created between 
the outer surface of the armature core and the polar faces, 
whilst the interior space within the core remains almost en- 
tirely free from lines of force. 

The drum or Siemen's type of armature differs essentially 
from the ring armature only in the manner in which the con- 
ductors are arranged upon the iron core. In the ring arma- 
ture the core consists of a ring, and is overwound with con- 
ductors passing along the outer surface and through the 
interior ; in the drum armature, the core is in most cases a 
ring also, or may be regarded as a ring, and is overwound 
with conductors passing along the outer surface, but in place 
of passing through the interior the conductors are carried 
completely around it axially, in the manner represented in 
Fig. 127. 

This shows a drum armature in perspective, upon which 
only two adjacent conductors or coils have been wound. 
Since the windings of the drum armature pass over the ends 
of the core, it is impossible to represent the whole of them in 
perspective, and, therefore, they are exhibited diagramatically 
in Fig. 128, which illustrates what is known as a right-handed 
winding, with eight-part commutator (see in cut a, b, c, d, 
etc.). In the figure shown, the windings are supposed to be 



i 



NEW CATECHISM OF ELECTRICITY. 



299 



WINDING OF ARMATURES. 

viewed from the commutator or front end of the armature. 
The windings passing along the length of the drum are 
represented by the small circles upon which are marked 

the dots and crosses de- 




\ 



L X. 




Fig. 127. 



noting the direction of 
the K. M. F., as in the 
ring armature. The con- 
nections passing across 
the back end of the drum 
are represented by the 
dotted lines ; those upon 
the front end by full lines. 




300 NEW CATECHISM OF ELECTRICITY. 

WINDING OF ARMATURES. 

The manner in which the individual loops or coils are 
arranged will be rendered clear by following the course of a 
single loop or coil upon the armature. 

Starting from the commutator segment (a) upon which the 
positive brush is resting at the upper portion of the armature, 
the conductor proceeds up the face of the drum to b, thence 
along the top and across the back end to the lowest part of 
the drum, from whence it proceeds across the bottom of the 
drum to 15. From 15 the conductor is brought around the 
face of the drum and connected to the commutator section 
(h), next to the one from which it started. 

Another coil starts from the segment (h) and follows a 
similar course upon the surface of the armature, and is con- 
nected to the segment (g), from which another coil starts, 
and so on all around the armature. A continuous closed spiral 
is thus formed all around the armature, in a somewhat similar 
manner to the ring armature. The arrangement of the line 
of force in the magnetic field, when the armature is inserted 
therein, is similar to that of the ring armature, and with the 
armature rotating in the direction indicated by the arrow, it 
will be seen that the K. M. F.s and currents induced in the 
conductors, on either side of the armature, have the same 
relative directions as those induced in the conductors arranged 
upon the outer surface of the ring armature, the only differ- 
ence being that the current flows across each end of the drum 
in place of flowing through the interior ; the conductors at 
the ends being thus the only idle portions of the winding in 
the drum armature. 



NEW CATECHISM OF ELECTRICITY. 3OI 



WINDING OF FIELD MAGNETS. 

Field Magnet Windings. — The insulated wires used for 
the excitation of the field magnets, not being subjected to any 
of the detrimental influences experienced by the armature 
conductors, are in most cases of solid copper. As a rule, the 
wires are wound upon insulated spools, which are afterwards 
slipped over the limbs of the magnet ; in some cases, however, 
they are wound direct upon the core of the field magnet, this 
latter being previously insulated with vulcanized fibre or other 
insulating material. 

In general, the wires used for the exciting coils of shunt 
wound dynamos are very thin ; hence, when this is used for 
making connection to the terminals of the machine, it is very 
liable to break off near the flanges of the reel upon which it 
is wound. 

Several plans are adopted to prevent this occurring : in 
some cases the ends of the shunt coils are soldered to stouter 
wires within the flanges of the bobbins, these wires being 
afterwards connected to the terminals of the machine ; in 
other cases, the ends of the coils are soldered to large termin- 
als fixed upon the flanges of the bobbins, these terminals 
being afterwards suitably connected together by strips of 
copper. 

Ring Windings. — When a ring core is to be wound, it is 
frequent to stencil upon the end faces a number of radial 
lines corresponding in breadth to the separate sections, so as 
to guide the winder in his work. 



302 



KEW CATECHISM OF ELECTRICITY. 



Fig. 129. 



RING WINDINGS. 

For ring-windings there is, in general, little trouble. 
Nevertheless, some care must be exercised. The separate 
" sections" of the coil are almost invariably wound on the 
cores separately, leaving the ends projecting, secured tempor- 
arily with string, and these ends subsequently connected to- 
gether and to the commutator. An inexperienced workman 

may easily connect up wrongly ; 

making a left-handed winding 

instead of a right-handed one, or 

vice versd. 

Hence, it is well to provide him 
with some such working drawing as 
Fig. 129, which relates to a right- 
handed winding having four turns 
in each section. The wire marked 
" o " is the last or outer end of the 
section previous to that considered. 
This end will eventually be brought 
down to a bar a of the commutator, and from this bar will go 
out the beginning or left-bottom end, marked L, B, of the 
section in question. L/Ooking at this diagram the winder 
will see that the wire ly B must pass under the core to the 
far end and then return over the top, thus making turn No. 1. 
It will then bend down to the right, be threaded through again, 
and make turn No. 2 ; again, and make turn No. 3 ; but as 
the inner space is narrower than the outer space, turn No. 4 
will probably have to ride on, or partly bed between, the turns 
already wound. The right-top end, marked R T, will eventu- 




Winding Diagram. 
Armature. 



NEW CATECHISM OF ELECTRICITY.. 303 

RING WINDINGS, ETC. 

ally be joined to bar h of the commutator. If the winder is 
shown that the right- top wire of one section joins the left- 
bottom turn of the next section at the commutator, he will 
have no excuse for mistakes. The winding of multipolar 
rings is absolutely similar, provided as many brushes are 
applied to the commutator as there are poles. 

For arc-lighting armatures, and in general those which 
have numerous convulutions of wire to each section, it is con- 
venient to prepare the wire in separate lengths sufficient for 
each section, and to coil each length on small shuttles each 
length being wound upon two shuttles, which are alternately 
used for successive layers. By this device both ends of the 
wire that constitutes a section are brought to the outside in- 
stead of one of them leading directly down to the bottom 
layer, as in ordinatry bobbin winding. 

Winding Diagrams. — If one tries to draw all the con- 
nectors of a drum winding the lines cross and occasion con- 
fusion. There is therefore a great advantage in adopting a 
mode of representation, originally suggested by Herr Fritsche, 
of Berlin, in which the armature winding is considered as 
though the entire structure had been developed out on a flat 
surface. 

If one was to attempt in a picture to show twenty or more 
conductors and their respective connections, the drawing 
would be unintelligible. Accordingly we have to imagine 
ourselves placed at the centre, and the panorama of the four 



304 



NEW CATECHISM OF ELECTRICITY. 



ARMATURE WINDINGS. 



Fig. 130. 




DEVELOPMENT OF WINDING EOR FOUR POLE MACHINE. 



NEW CATECHISM OF ELECTRICITY. 



305 



ARMATURE WINDINGS. 




WINDING FOR FOUR POLK MAGNET TO 
CORRESPOND TO FIG. 130. 



306 NEW CATECHISM OF ELECTRICITY. 

ARMATURE WINDINGS. 

poles laid out flat, as in Fig. 130. It will be noticed that the 
faces of the N and S poles are shaded obliquely for distinc- 
tion. 

Now in an actual machine there are many armature con- 
ductors spaced symmetrically around, and these have to be 
grouped together by connecting wires. In the case of ring 
windings the wires which connect the active conductors in the 
gap-space pass through the central aperture in the ring when 
they are removed from the magnetic field. Suppose, for 
simplicity we have a ring armature of only 12 turns and 12 
bars to the commutator. If this is opened out from the in- 
side we shall have the form shown in Fig. 130, where the 
dotted lines are the inactive parts of the spiral winding that 
pass through the inside of the ring. 

By tracing the arrows it will be seen that there must be 
two positive and two negative brushes. Fig. 131 gives an end 
view diagram of the same winding by which the two modes of 
presentation may be compared. It is usual to couple the 
positive brushes together, and the negative brushes together. 
A 6-pole machine would require six brushes, and so forth. 
When the brushes of the same sign are thus connected 
together the electromotive-force of the whole armature is 
simply that of any of the sets of coils from one -|- brush to 
the adjacent — brush. 

Lap Winding and Wave Winding. — This distinction arises 
in the following manner. Since the conductors that are 
passing a north pole generate electromotive-forces in one 



NEW CATECHISM OF ELECTRICITY. 307 

ARMATURE WINDINGS. 

direction, and those that are passing a south pole generate 
electromotive -forces in the opposite direction, it is clear that 
a conductor in one of these groups ought to be connected to 
one in nearly a corresponding position in the other group, so 
that the current may flow down one and up the other in 
agreement with the directions of the electromotive -forces. If 
now we examine Fig. 132 we shall see that at the back of the 
armature (or end distant from the commutator) each con- 
ductor is united to one five places further on — No. 1 to No. 6, 
No. 3 to No. 8 — and that at the front end the winding, after 
having made one " element " (as for example d-j-12-e), then 
forms a second element (^-9-14-/"), which laps over the first ; 
and so on all the way round until the winding returns on 
itself. 

Now contrast with this Fig. 133, in which, though the 
connections at the back end are the same, those at the com- 
mutator end are different. . It will be seen that when the 
winding returns back toward the commutator, instead 
of lapping back toward the part from which it started, 
it is turned the other w r ay. The winding d-y-12 does not 
return at once to e, but goes on to /, whence another element 
z-17-4-^ goes on in a sort of zig-zag wave. These are both 
drum windings, the corresponding winding tables being as 
shown in Figs. 134 and 135. 



Note. — As each and every armature must needs have its own especial 
winding— based, of course, upon both experience and calculations, it will 
be understood that these few pages are given to explain the general 
practice— and in no other sense. 



303 



NEW CATECHISM OF ELECTRICITY. 



ARMATURE WINDINGS. 










Fig. 133. 



NEW CATECHISM OF ELECTRICITY. 



309 



ARMATURE WINDINGS, 




§ 

I 

is 



I 



Fig. 133. 



3io 



NEW CATECHISM OF ELECTRICITY. 



ARMATURE WINDINGS. 

Figs. 134 and 135 represent tables such as are furnished the 
practical workmen by the designers of the machines. These 
greatly facilitate the work and add accuracy to the building of 
the dynamo. 

(Wave- winding. ) 



F 


B 


F 


a 


1 


« 1 / 


f 


11 


10 b 


b 







8 


(I 


— 9 


13 


IS 


c 


c 


5 


10 


h 


h 


15 


2 


a 


d 


7 


12 


i 


i 


17 


4 


e 


+ e - 


9 


14 


a 



Fig. 134. 
(Lap- winding} 



F 


B 


F 


-%-a 


1 


6 


b 


b 


3 


8 


c 


~*~ c 


5 


10 


d 


a 


7 


12 


e 


+ e 





14 


f 


f 


11 


10 





— v 


13 


18 


h 


h 


15 


2 


i 


i 


17 


4 


a 



Fig. 135. 



NEW CATECHISM OF ELECTRICITY. 



311 



TESTING FOR CONDUCTIVITY AND 
INSULATION. 



Testing for Conductivity. — In making this test, the instru- 
ments are connected as represented in Fig. 136. B is the bat- 
tery, G the galvanometer, and S is a coil of wire being tested 
for electrical continuity or conductivity. As will be seen, the 

Fig. 136. 




positive pole -|- of the battery is connected to one terminal of 
the galvanometer, and the other or negative pole is connected 
to one of the ends of the coil under test. The other terminal 
of the galvanometer is connected to the other end of the zoil. 
If the connecting wires are making good electrical contact 



312 



NEW CATECHISM OF ELECTFICITY. 



TESTING FOR CONDUCTIVITY. 

with the respective terminals, and the wire of the coil being 
tested is unbroken, the needle of the galvanometer will be de- 
flected as soon as a closed circuit is made by the end of the coil 
coming into contact with the galvanometer terminal. If the 
wire of the coil is broken in some part or the ends of the con- 

Fig. 137. 



*Hi I I I I h 




6 




necting wires do not make good electrical contact with the ter- 
minals, the needle will not be deflected. In order to prevent mis- 
takes, it is advisable to test the battery and galvanometer con- 
nections and contacts by short circuiting or bringing the ends 
of the wire connecting the terminal of the galvanometer and 
negative pole of the battery together before starting to test 
the circuit or coil. If the needle is deflected, the connections 
are all right ; if undeflected, there is a bad contact some- 
where, which must be made good before the test can proceed. 



NEW CATECHISM OF ELECTRICITY. 313 

TESTING FOR CONDUCTIVITY. 

Testing for Insulation. — The o1>ject of this test is to ascer- 
tain whether the insulation of a circuit or of the wire wound 
upon a metal spool or core, such as a magnet core, has broken 
down or is in good order. In making the test, the instru- 
ments and connections are arranged as shown in Fig. 137. 
The battery and galvanometer are connected to one another, 
as in the conductivity test described above. The unconnected 
terminal of the battery is connected to one end of the coil 
under test, the other end of the coil remaining free and 
unconnected. Some portion of the metal core, say the end, 
is then cleaned bright with a knife or emery cloth, and the 
unconnected terminal of the galvanometer is brought into 
contact with this bright or clean part of the core. If then 
some portion of the insulation of the wire has been abraded or 
destroyed, thus bringing the bare wire into contact with the 
metal core, as at A in the figure, the needle of the galvano- 
meter will be deflected since a closed circuit is formed through 
the core and wire. If on the contrary the insulation is per- 
fect, the needle will be undeflected. It will thus be seen that 
in the conductivity test it is necessary that the needle should 
be deflected, or turned, to prove that all is right, while in the 
insulation test the converse holds good ; if the needle is de- 
flected, it proves that the insulation is broken down. 



NEW CATECHISM OF ELECTRICITY. 



Fig. 138. 




NEW CATECHISM OF ELECTRICITY. 315 



THE ALTERNATOR. 



A dynamo constructed without a commutator for making 
the current direct, produces an alternating current, and such 
a machine is called an alternator. A great many kinds of 
alternators have been constructed. They may be thus classi- 
fied : 

1. Those with a stationary field magnet and rotating ar- 
mature. 

2. Those with rotating field magnet and stationary arma- 
ture. 

3. Those with both field magnet and armature part station- 
ary. 

In the latter class, the amount of magnetic induction from 
the armature to the field is caused to vary or alternate in 
direction by the revolution of appropriate pieces of iron called 
inductors. Still another division rests on whether they give 
one simple alternating current, a two-phase current, or 
whether they give multiple currents. 

In alternate-current working machines, the current is 
rapidly reversed, rising and falling in a succession of impulses 
or waves. Electricity is, in fact, oscillating backwards and 



3l6 NEW CATECHISM OF ELECTRICITY. 

THE ALTERNATOR. 

forwards through the line with enormous rapidity, under the 
influence of a rapidly-reversing electromotive-force. 

The adjectives alternate, oscillatory, periodic, undulatory 
and harmonic have all been used to describe such currents ; 
the term wave-currents is more apt. 

The properties of alternate-curreuts differ somewhat from 
those of direct or continuous currents. They are affected not 
only by the resistance of the circuit but also by its inertia it 
self-induction, which diminishes the amplitude of the waves 
and retards their phase. 

The alternating current enables us to take advantage of an 
effect called induction, which is only exerted when the cur- 
rent is suddenly broken or changed in direction. 

The ordinary alternator has three or more pairs of poles 
instead of a single pair, and the armature carries as many 
coils as there are poles. These coils are coupled in series or 
in parallel so as to act as a single coil, the large number of 
poles increasing the number of alternations or cycles per 
second. Since alternating currents are used largely for light- 
ing, it is necessary to have at least forty complete alternations 
per second in order to avoid flickering of the incandescent or 
arc lights. 



Note. — The alternating current machine may be built to give directly 
a pressure up to 2,000 or 3,000 volts, and in certain types as high as 5,000 
volts. If this is insufficient for the purpose, the voltage may be still 
further increased by the use of transformers. 






NEW CATECHISM OF ELECTRICITY. 317 

THE ALTERNATOR. 

Also, the transformers would have to be much larger if the 
frequency of alternations were less. For the systems in gen- 
eral use, sixteen thousand single alternations (eight thousand 
complete alternations or cycles) per second have been adopted 
as giving the most desirable frequency, the recent tendency 
being to reduce this to a considerably lower number. With a 
single coil armature revolving in a two-pole field, this would 
involve excessively high speed, hence the necessity for the 
mnltipolar field. 

Multiphased currents are two or more separate and dis- 
tinct currents not differing in any way from the current de- 
rived from an ordinary "single phase" alternator. Their 
peculiarity lies, not in the nature of the currents themselves, 
but in the fact that they have different strengths at a given 
instant of time. 

In the two-phased system, for instance, when one of the 
currents is at zero value, the other has its maximum value, or 
the currents are displaced in phase, whence the expression 
two-phased. 

If two identical simple alternators have their armature 
shafts coupled in such a manner, but when a given armature 
coil on one is directly under a field pole, the corresponding 
coil on the other is midway between two poles of its field, 
the two currents generated will differ in phase by a half- 
alternation, and will be two-phased currents; similarly, three- 
phased currents could be generated by coupling the armatures 
of three simple alternators so that the corresponding coils on 
each are equally " staggered " with respect to each other. 



318 NEW CATECHISM OF ELECTRICITY. 

THE ALTERNATOR. 

By the introduction of what is known as the tnulti- phase 
systems all difficulties have been overcome and alternating 
current motors are now manufactured which are equal to the 
best direct current motors in efficiency and starting torque, 
and which have the additional advantage of having no com- 
mutator or moving contacts of any kind. 

Two-phase and three-phase currents differ in this respect ; 
the two-phase system requires four wires to connect the gen- 
erators with the motors and their action is that of two distinct 
and separate circuits through which are passing simple alter- 
nating currents of electricity which act upon the revolving 
part of the motor like the two cranks on a cross connected 
engine at right angles to one another, or one 90 degrees in 
advance of the other. 

The three-phase method of employing the alternating cur- 
rent requires only three wires and for transmitting electrical 
energy in large amounts long distances for power purposes, 
it is an ideal system. 

The Monocyclic System. — The " monocyclic " system is that 
in which three wires are used, but the main or energy current is 
conveyed by two of the wires, while the third one serves as an 
auxilliary and is necessary for starting the motor. The 
motors are of the class called "induction motors " from the 
fact that the current in the armature or revolving part is in- 
duced by an alternating current in a stationary coil outside of 
the armature and at an angle to the field, instead of being con- 



Note. — The Fig. on the next page is intended to show the "wave 
motion ' ' of the different alternations. 



NEW CATECHISM OF ELECTRICITY. 



319 



THE ALTERNATOR. 

ducted into the armature through sliding contacts as in the 
more familiar direct current motor. 

Motors constructed upon this principle have the advantage 
of great starting power, and are able to stand temporary over- 
loads without damage. They can be made smaller than the 
direct current type, are cylindrical in shape and adapted to be 
put in any position. They are almost as simple as a grind- 
stone, and having self-oiling bearings, require scarcely any 
attention at all. 

The monocyclic in its broadest sense is a combination of 
the single-phase and three-phase systems. Three-phase cur- 
rents are produced from single-phase currents by means of a 
specially wound armature which may be operated as a motor- 
generator at the point where energy for motors is to be dis- 
tributed, or the main generator may be provided with a special 
armature arranged to produce the necessary difference of 
phase between the ordinary two-wire circuit and a third wire. 




320 NEW CATECHISM OF ELECTRICITY. 



MOTORS. 



Very nearly all that has been said upon the subject of 
dynamos applies to the motor and needs not to be repeated. 
Motors are, however, divided into two general classes : 

i. Those for use with continuous currents. 

2. Those for use with alternating currents. 

The real development of the motor as a transmission of 
power machine came after the commercial introduction of 
Gramme's dynamos in 1871, as engineers began to understand 
how two of these machines could be used — one as generator, 
the other as motor — to transmit power through a line. All 
the earlier attempts to introduce electric motors came to 
nothing, for at that time there was no economical method of 
generating electric currents known. 

But, motors are also classified the same as dynamos, as 
series wound, shunt wound, compound wound, bipolar and 
multipolar motors. The motor being intended for the distri- 
bution and application of the power generated by the dynamo 



Note.— A glance at the early history of the electric motor brings out 
the striking fact that this machine was invented eight years before the 
dynamo, and for several decades it was considered of more importance, 
both scientifically and practically. 



NEW CATECHISM OF ELECTRICITY. 



321 



MOTORS. 

is usually a much smaller machine — thus a dynamo of 1,000 
horse power will furnish the necessary force for nine or ten 
100 horse power motors. 

In construction, the dynamo and motors are essentially the 
same, but in their action are exactly the reverse. 



Fig. 139. 





GENERATOR. 



MOTOR. 



Motors depend for their operation on the tendency to 
motion in a magnetic field. 

If the conducting wire, while situated in the magnetic field, 
is actually conveying an electric current (from whatever 
source) it experiences a side thrust, tending to move it forci- 
bly, parallel to itself, across the magnetic lines, and so enables 
it to exert power and to do work. This is illustrated in Fig. 



322 NEW CATECHISM OF ELECTRICITY. 

MOTORS. 

140, where the small arrows exhibit the movement of the cur- - 
rent and the large arrow the resulting push or magnetic force. 

This action is the principle of the dynamo used as a motor. . 

Two points are vital to the right understanding of the* 
action of electric motors: (1) the propelling drag, (2) the- 
Counter electromotive-force. The first is that the real driving- 
force which propels the revolving armature is the drag which 
the magnetic field exerts upon the armature wires through 
which the current is flowing (or, in the case of deeply-toothed 
armatures, on the protruding teeth): the second is that the 
revolving armature generates a counter electromotive force as 
its moving wires cut the magnetic lines. 

Fig. 140. 




The Propelling Drag. — In a generator the drag acts in a, 
direction which opposes the rotation, and is, in fact, a counter- 
force or reaction against the driving force. In a motor the : 
drag is the driving-force, and produces the rotation. 

The Counter Electromotive-force. — Let it be remembered 
that wherever in an electric circuit, current flows through 
some portion of the circuit in which there is an electromotive- 



NEW CATECHISM OF ELECTRICITY. 323 

DYNAMO AND MOTOR BELTS. 

force, the current will there either receive or give up energy 
according to whether the electromotive-force acts with the 
current or against it. This will be made clearer by Fig. 139, 
representing a circuit in which there are a dynamo and a 
motor. Each is rotating right-handedly, and therefore gen- 
erates an electromotive-force tending upwards from the lower 
brush to the higher. In each case the upper brush is the posi- 
tive one. But in the dynamo, where energy is being supplied 
to the circuit, the electromotive-force is in the same direction 
as the current ; whilst in the motor where work is being done, 
and energy is leaving the circuit, the electromotive-force is in 
a direction which opposes the current. 



DYNAMO AND MOTOR BELTS. 



" Points" relating to Dynamo and Motor Belts, — No sub- 
ject relating to motors will be found of more practical interest 
than the following : 

1. Dynamo belts should make a straight run through the 
air and over the pulleys without wabbling ; they should main- 
tain an even and perfect contact with that part of the pulley 
with which they come in contact. In order to do this they 
should be kept soft, pliable, and have no abrasions or rough 
places — the belt should be first-class — as near perfection as 
possible, for they must do their work so the light burns with- 



324 NEW CATECHISM OF ELECTRICITY. 

DYNAMO AND MOTOR BELTS. 

out flicker. When belt fasteners give way there is too much 
strain upon belt. The greatest amount of slack in a belt is 
found when it leaves the driving pulley, hence the tightener 
should be near the driving pulley, as it takes up the slack, 
prevents vibration and diminishes strain on belts and bear- 
ings. More than no° of heat is injurious to belts. 

2. The double belt should always run with the splices, and 
not against them. One-quarter turned belts should be made 
of two-ply leather, so as to avoid so much side strain. Slow- 
motion belts should be made of two-ply leather, as they 
receive hard labor and strains. 

3. The electric generators of the alternating system require 
special belts, as they are run at great velocity. Belts for the 
alternating system should be endless, perfectly smooth, even in 
texture and thickness. If too much power is added to the stick- 
ing or adhesive qualities of a belt the friction will cause loss. 

4. Friction is greatest when the pulleys are covered with 
leather. Friction depends upon pressure, but adhesion 
depends upon the surface contact ; for instance, two square 
feet of adhesion will hold twice as much as one square foot, 
hence, the more a belt adheres to pulley surface without 
straining, through too much tightening, the better the driving 
power. Wet days produce slipping because the leather absorbs 
dampness. 

5. A leather-covered pulley will produce more resistance 
than polished or rough iron ones. A good belt dressing makes 
a smooth, resisting surface, and as it contains no oils, which 



NEW CATECHISM OF ELECTRICITY. 325 

DYNAMO AND MOTOR BELTS. 

create a slippery surface to belts, it increases belt adhesion. 
The friction of leather upon leather is five times greater than 
leather upon iron. 

6. Moisture and water distend the fibres, change the 
properties of the tanner's grease and softening compounds. 
Repeated saturation and drying will soon destroy leather. 
Leather well filled with tanner's grease or animal oil, if 
allowed to hang in a warm room for several months without 
handling, will dry out, become harsh, and will readily crack. 

7. Many things have been used to make belts stick to the 
pulleys, some of considerable value. A careful study of all the 
parts that work together is required in order to get full power 
transmission. Suitable belt dressing will overcome many 
serious questions that arise, but it must be properly applied. 

8. A running belt is stretched and relaxed at different 
times, and unless there is perfect elasticity in all its parts 
there will not be uniform distension. Whatever relieves the 
strain upon belts prolong their life. There should be 25 per 
cent, margin allowed for adhesion before a belt begins to slip. 

9. The adhesion between the surface of belt and pulley 
must produce more friction than the pull or tension. When 
great tension or stretching is required it evidences the fact 
that the belt is not properly proportioned, or that it is oil 
soaked and there is too much oil on the pulleys. 

10. An endless belt will always give the best results, as 
lacing produces a momentary flicker in the lights at each 
revolution. 



326 



NEW CATECHISM OF ELECTRICITY. 



ELECTRICAL POWER TRANSMISSION. 



As compared to any other known method of transmitting 
power it may be said that electricity is an ideal agent, for as 
it has been well said — 



Fig. 144. 




LINK WORK. 



Electricity never stretches, never breaks, 
weighs nothing, can be subdivided indefinitely 
with great ease, can turn corners without loss. 
It can transmit large amounts of energy at 
pressures easily controlled along wires of mod- 
erate size, and it never freezes. Its loss by 
friction is comparatively insignificant, and its 
other losses in compariscn with every other 
known agent are almost nothing. 

The period of planning the schemes of 
transmission, of designing the dynamos, and of 
construction is now ended and all criticism as 
to dividends on the cost of electric works has 
been swept away by the results achieved. The 
efficiency of each type of machine and system 
is now greater than has been attained before. 
and definite results are assured. 



NEW CATECHISM OF ELECTRICITY. 327 

ELECTRIC POWER TRANSMISSION, 

A system for the transmission of electric energy embraces: 
First, a conducting circuit between the two stations. Second, 
a battery or dynamo arranged to furnish the current. Third, 
the motor for changing the electric back into mechanical 
energy. 

Electric transmission can be used to advantage with 
standard forms of machines as follows : 

First, where a large waterpower is available at a considera- 
ble distance from the mill which is in need of more power 
than can be obtained from the water privilege at the mill 
itself. 

Second, where owing to the separation of mill buildings, 
or peculiar local requirements, it is desired to transmit power 



Note. — The waters of the American River, which have been running 
to waste, are now utilized for lighting Sacramento's streets, propelling her 
cars, operating her factories and cooking the food of her citizens. Years 
have been spent on the work here. An immense masonry dam was 
thrown across the American River at Folsom, California, creating a 
reservoir three miles long and furnishing a flow of 85,000 cubic feet a 
minute. The water, after passing through four horizontal shaft double 
turbine wheels, is used for irrigation purposes, and 300,000 acres of land 
will be supplied. The turbine wheels are 30 inches in diameter, and 
under a head of 55 feet develop 1,300 horsepower each. The shafts of the 
wheels are coupled direct to the shafts of four three-phase alternating 
current generators of the General Electric type, each capable of develop- 
ing 1,000 horse-power. These dynamos weigh about forty tons each. 
The electric current is passed through " step-up " or raising transformers 
which raise the voltage to 16,000 volts, and it is then transmitted by over- 
head copper wires to this city. 

Two separate lines have been built as a precaution against accident or 
shutdowns for repairs. One line will always be held in reserve. It is 
calculated that 50 per cent of the electric power generated at Folsom will 
be transmitted twenty-four miles to Sacramento, 



328 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC POWER TRANSMISSION. 

further than can be done by belting in order to avoid the 
instalment of individual steam plants in each building. 

Third, where small water privileges are available at various 
points on a stream, but in order to become useful the power 
must be concentrated at one point without too great expense 
for maintenance and operation of the individual parts of the 
system. 

Fourth, where for various reasons in securing a mill site 
it is desirable to locate at a considerable distance from the 
source of power on account of the fact that the land immed- 
iately adjacent to the privilege is not suitable for location. 

Fifth, where for special reasons it is important to do away 
with shafting throughout the mill. 

Electric motors in the machine shop work so satisfactorily 
for power transmission and effect such evident savings in the 
cost of manufacturing that they are utilized in many ways. 
The motors used average about 3 H. P. and are connected by 
insulated wires strung to switches located at convenient points 
about the shop. No pains are taken to fasten the motors 
while they are at work, as their own weight is amply sufficient 
to hold them in position and keep the belt tight. 

The great convenience of moving tools and placing them 
in any desired position is a great advantage of the new 
system. 



Note.- The great adaptability of this system was well shown in the 
case of a factory which was almost completely destroyed by fire, neverthe- 
less a few uninjured tools in a remote end of the building were operated 
successfully by means of electric motors within two days after the fire. 



NEW CATECHISM OF ELECTRICITY. 329 

ELECTRIC POWER TRANSMISSION. 

Practically the only objection which can be urged against 
the electric system of transmission is the fact that the first 
cost of installation is greater than with ordinary belting and 
shafting, but even this is questionable, since while it might seem 
that the electric system would actually consume more power 
than the ordinary plan since it involves two transformations 
of energy. In most cases, however, if the power has to be 
distributed to a number of machines, particularly if they are 
located at any distance from the engine, the loss of power is 
less with electric transmission. This is explained by the high 
efficiency of the dynamo and motor compared with the low 
efficiency of belt transmission as ordinarily practiced. Perhaps 
the greatest saving, however, of the electric system is due to 
the fact that the consumption of* energy entirely ceases when 
the tool stops. This stoppage in the case of the busiest tools 
amounts to at least 25 per cent, of the nominal working hours 
throughout the year and with large or special tools which are 
not used so steadily, the stoppage is often as high as 50 to 75 
per cent, since there are many whole days when they are not 
used at all. 

Wherever electric motors can be substituted for a number 
of small engines scattered about, the saving in power is very 
great not only because of the low efficiency of small steam 
engines, but also by the avoidance of condensation in long 
steam pipes. 

Perhaps the most important advantage gained by the 
electric system is in the increased output since the cost of 
power is a very small item. This increased output is secured 



33° NEW CATECHISM OF ELECTRICITY. 

ELECTRIC POWER TRANSMISSION. 

by the greater convenience and promptness in starting and 
stopping as well as in regulating the speed of the machinery. 
The workman can, for example, temporarily increase the 
speed, when conditions are favorable, thereby saving consid- 
erable time. 

The ordinary type of motor used in factories is the plain 
shunt wound machine fed with constant potential current. 
The motor is started and varied in speed by means of a rheostat 
in the armature circuit. This simple arrangement answers 
very well in most cases, but for variable speed between wide 
limits a series wound motor controlled by a rheostat as in 
electric railway practice may be preferable. In other cases 
some special method of regulation such as the Leonard system, 
or the " boost and retard " plan may be adopted. 

Electrical Transmission in Mines. — It is predicted that 
the day is not far distant when every large mine in the 
country will have adopted electric power, and that such 
adoption, in view of superior advantages for continuous 
service, as shown in the record of the Mammoth mine outfit, 
will result in the more general use of convenient water 
power. 

The utilization of water power electrically transmitted for 
mine operation is becoming more popular among mining 
men, as each installation demonstrates not only the feasibility 
of the system but also the economy which every such installa- 
tion shows when compared with pre-existing systems which 
it displaces or which are in similar operation elsewhere, 



NEW CATECHISM OF ELECTRICITY. 33I 



ELECTRIC POWER TRANSMISSION. 

Long Distance Electrical Transmission. — In a general 
way, at the usual price of coal, the transmission of power from 
cheap water power, up to ten or fifteen miles, will nearly 
always pay, if the amount be reasonably great, a few hundred 
or a thousand horse power ; while the current can readily be 
transmitted over enormously great distances — several hundred 
miles — practically speaking, such transmissions will probably 
be exceedingly rare for many years to come. 

Admitting that power can be transmitted satisfactorily, the 
next point is as to the economy of this electric transmission. 
In the cost of a water privilege at a distance, where the 
problem is to transmit power in bulk for a few thousand feet 
or more, the practical question is simply one of cost of power 
delivered on the ground by steam. The cost of power de- 
livered to the motors, of course, depends upon the value of 
the water privilege, its cost to electrical apparatus and local 
conditions. 



Note. — The project is now discussed in England to supply electric 
power from central stations built in the centre of the coal fields and 
transmit it to the great industrial centres, including I/mdon, where 
transmitting and storage stations could be erected. The electric energy- 
could be sold to the different distributing companies at a little over two 
cents per kw hour and to the small factory owner for about $25 per 3,000 
working hours for one H. P.; in I^ondon this costs at present about twice 
as much ; the system enables valuable chemical constituents to be re- 
covered from the coal, which at present cannot be done in the smal 
steam power plants ; one of these constituents is sulphate of ammonia ; 
it is estimated that one H. P. hour can be obtained for %. pound of coal, 
the average consumption at present being 5 pounds ; the loss in trans- 
mission from the coal fields to London is about 33 per cent. ; for trans- 
mitting 10,000 H. P., three bare conductors for the positive and three for 
the negative would be used and run on oil insulators ; 30,000 volts are to 
be used. 



332 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC POWER TRANSMISSION. 

As regards the difficulties which have to be encountered in 
electrical power transmission, the principal ones centre about 
the transmission line. Speaking from an electrical stand- 
point, it is sometimes difficult to get and maintain insulation 
against the voltages put to use for long distance work. 
Physically the maintenance and guarding of a long line 
against accidents, or malicious injury, is not altogether easy 
to be paid. The difficulties include such things as severe 
storms, which tear down the line, or blow down trees across 
it, accidental or malicious breaking of insulators and the like, 
to say nothing of the ordinary wear and tear to which over- 
head lines are subjected. Quite aside from such special 
causes of damage, the generation and utilization of power is 
all clear sailing. 

Economy of Electric Locomotives. — Under certain condi- 
tions no doubt exists as to the economy of electrical appli- 
ances. In the saving in repairs it is stated on the authority 
of Siemens that the electric locomotives on the underground 
railway in I/ondon ran 60,000 miles without needing repairs of 
any kind. In the wear of tracks, in lighter road-beds and 
bridges and in steeper grades, the economies from this stand- 
point are beyond peradventure. The building of electric 
power stations of smaller capacity than the aggregate capacity 



Note. — 5,000, 10,000 or 15,000 volts is within the range of fair practi- 
cability if the climatic conditions are favorable. I would not hesitate to 
make it 30,000, 40,000 or 50,000 volts, in a climate like that of some parts of 
Mexico, while I would shun half of this, in a stormy or damp climate- 
Prof. Bell. 



NEW CATECHISM OF ELECTRICITY. 333 

ELECTRIC POWER TRANSMISSION. 

of locomotives, and the saving in coal consumption by work- 
ing steam economically in large cylinders are placed in the 
favor of electric traction. 

These remarks apply very nearly to all forms of electric 
transmission. 

The Niagara Falls Power Plant. — No enterprise of modern 
times has attracted greater attention from the engineers of 
the world and the public in general than the work which was 
undertaken some years ago by the Niagara Kails Power Com- 
pany for the utilization of a portion of the power of the 
Niagara, Falls through electric-motors operated by turbine 
water wheels. 

About 275,000 cubic feet of water pass over the falls each 
second, falling from the crest of the falls 165 feet, furnishing, 
as it has been estimated, not less than seven million of horse 
power. 

The surface canal starts from a point about one and one- 
half miles above the falls and runs inland 1,700 feet, with a 
depth of 12 feet, the main tunnel being 7,000 feet long, 19 
feet wide and 21 feet high. This artificial waterway has a 
capacity sufficient to develop 100,000 horse-power. 

This great work is under construction in what are called 
" units " of 5,000 electric horse power, several of which are in 
most successfnll operation. 



334 NEW CATECHISM OF ELECTRICITY. 



THE DYNAMOTOR. 



A dynamotor is an electrical apparatus in which two ma- 
chines, a dynamo and a motor, are placed on the same shaft, 
one of the machines receiving current, and the other gene- 
rating current, usually of a different voltage. 

In one form two armatures are mounted on one shaft in a 
single field or in separate fields ; one is a motor armature 
driven by the original current ; the other generates new cur- 
rent. This is a "motor-dynamo," and it can transform con- 
tinuous currents up or down. 

Continuous current transformers have attained an effi- 
ciency of 83 per cent, at full load. 

Another form of dynamotor is called the continuous alter- 
nating transformer. This is arranged so as to change a con- 
tinuous into an alternating current or the reverse. 

As the driven and driving parts of the dynamotor are 
contained in one rotating part, their friction is very slight. 



Note. — The long distance transmission lines for a certain railway are 
connected to step-down transformers, transforming the current from 
6,000 volts on the line to 400 volts at the secondaries. The secondaries are 
connected to the three collector rings on one side, and the current is thus 
brought into the armature of the rotary converter or dynamotor. The 
alternating current at 400 volts is then converted in this machine into 
direct current at 500 volts at no load and 550 volts at full load delivered 
from the commutator side. This is given as example of the utility of the 
dynamotor. 



NEW CATECHISM OF ELECTRICITY. 



335 



TRANSFORMERS. 



For the sake of economizing the cost of the metallic con- 
ductors, distribution of the electric current is effected at a 
high electric pressure from the central generators, and is re- 




Fig. 142. 



ceived at different points by apparatus known as transformers, 
which transform the electric energy supplied to them, and 
give it out again at a lower pressure. 



336 



NEW CATECHISM OF ELECTRICITY. 



TRANSFORMERS. 

To comprehend fully the bearing of the matter, it must be 
remembered that the energy supplied per second is the pro- 
duct of two factors, the current and 
the pressure at which that current 
is supplied ; the magnitudes of the 
two factors may vary, but the value 
of the power supplied depends only 
on the product of the two ; for ex- 
ample, the energy furnished per 
second by a current of 10 amperes 
supplied at a pressure of 2000 volts 
is exactly the same in amount as 
that furnished per second by a cur- 
Fig. I4d. rent of 400 amperes supplied at 

a pressure of 50 volts ; in each case the product is 20,000 
watts. 




Now the loss of energy that occurs in transmission through 
a well-insulated wire depends also on two factors, the current 

and the resistance of the wire, 
and in a given wire is propor- 
tional to the square of the cur- 
rent. In the above example the 
current of 400 amperes, if trans- 
mitted through the same wire 
as the 10- ampere current, would, 
Fig. 144. because it is forty times as 

great, waste sixteen hundred times as much energy in heating 
the wire. Or, to put it the other way round, for the same 




NEW CATECHISM. OF ELECTRICITY. 



337 



TRANSFORMERS. 

loss of energy one may nse, to carry the io-ampere current at 
2000 volts, a wire having only T ^th of the sectional area of 
the wire used for the 
400-ampere current at 
50 volts. The cost of 
copper conductors for 
the distributing lines 
is therefore very great- 
ly economized by em- 
ploying high pressures 
for distribution of 
small currents. 



^- 1 








i 

11 


Hill 


1 fiflH 




si 
i 


1 


1 
111 



Fig. 145. 



Operation of the Transformer.- -If we wind two separate 
coils of wire on an iron bar, and pass a direct current through 
one coil, no effect is 



produced in the other 
coil except at the mo- 
ment of turning on the 
current, but if an alter- 
nating current is used 
instead, a current is at 
once produced and 
maintained in the sec- Fig. 146. 

ond coil. By a very simple law the pressure or voltage of the 
two coils are in proportion to the number of turns in each. 
Thus, if the primary coil is supplied with current of 1,000 
volts, and the secondary coil has one-tenth as many turns, 
the pressure in the secondary will be 100 volts. 




338 NEW CATECHISM OF ELECTRICITY, 

TRANSFORMERS. 

By the proper proportion of the primary and secondary 
coils, the voltage may be raised to any pressure which can be 
safely transmitted. 

Fig. 142 exhibits the transformer with its connecting 
wires and insulated. A transformer of the latest pattern may 
be said to have these points of excellence : 

High efficiency, close regulation, small leakage, quiet 
running, attractive appearance, convenient arrangement, 
separable core, removable coil, reliable fuse device. 

Fig. 145 and 146 represent two methods of procuring the 
necessary structure of laminated iron, the parts in this case 
being stamped from sheet iron. This is done to secure good 
magnetic circuit with ample ventilation. 

Fig. 143 is a representation of Farraday's first induction 
coil and is thoroughly typical of all transformers. 

Fig. 144 is another form of the cylindrical transformer and 
the one utilized by Ruhmkorfr is his special machine else- 
where described. 

For transforming from high pressures to low, several kinds 
of apparatus are known, namely : — 

1. Storage Batteries. — A large number of these to be 
charged in series at a high potential ; the series afterwards 
divided up or rearranged so as to discharge larger currents at 
lower pressure. This system is applicable to direct-current 
working only, not to alternate currents, and has the advantage 
of storing the consumer's supply. These will be treated on in 
a separate section. 



NEW CATECHISM OF ELECTRICITY. 339 

TRANSFORMERS. 

2. Induction Coils ', also called for this purpose Secondary 
Generatars, or Transformers, or Converters. — This system 
will only answer with alternating currents, which being trans- 
mitted through the distributing mains at high pressure, and 
traversing the primary wires of the induction-coils, set up in 
the secondary wires currents which feed the separate circuits 
of lamps at the desired low pressure. 

3. Motor-Generators as previously described. 

4. Commuting -Transformers. — These are a variety of the 
last, but neither armature nor field-magnet revolves, the 
polarity of the magnetic circuit being caused to vary by 
special commutators. 

5. Condensers. — It is theoretically possible to employ con- 
densers for transforming alternate currents, but their use is 
not yet practical. 



34° 



NEW CATECHISM OF ELECTRICITY. 



Fig. 147. 




INDUCTION COII.. 



Fig. 148. 




RUHMKORFF COIL,. 



NEW CATECHISM OF ELECTRICITY. 34I 



THE CONDENSER. 



This is a form (see Fig. 150) of accumulator which resulted 
from the discovery of the Ley den-jar. It is made of a num- 
ber of sheets of tin foil insulated from each other by sheets of 
paper soaked in parafine. The insulation may also be effected 
by the use of sheets of mica, oiled silk, etc. 

The telegraphic condenser consists of a box packed full of 
sheets of tin foil, the alternate sheets of which are connected 
with each other and each set has its own binding post. 

The tin foil is used in condensers because it is the cheapest 
for any two conductors which are near together and insulated 
from each other, acts as a condenser. The iron frame of a 
dynamo or motor and the wire wound upon the fields and 
armature act as the two surfaces of a condenser, and one may 
sometimes get a severe shock by touching both at the same 
time. A long insulated wire buried in the earth or in the 
water forms a condenser on account of the surface of the wire 
and the surface of water or earth outside being so large and so 
close together. 



Note. — The object of the condenser is, firstly, to make the break of 
circuit more sudden by preventing the spark due to self-induction in the 
primary circuit from leaping across the interrupter ; and, secondly, to 
store up the electricity of this self-induced extra-current at break for a 
brief instant, and then discharge it back through the primary coil so as to 
augment the induced direct electromotive-force in the secondary coil. 



342 



NEW CATECHISM OF ELECTRICITY. 



Fig. 149. 




ADJUSTABLE WATER RESISTANCE. 



Fig. 150. 



CONDENSER. 



NEW CATECHISM OF ELECTRICITY. 343 



INDUCTION COILS, 



An induction coil comprises three principal parts — the 
core, the primary coil, and the secondary coil. 

Induced currents have in general enormously high electro- 
motive-forces, and are able to spark across spaces that ordinary 
battery currents cannot possibly cross. The induction coil 
consists of a cylindrical bobbin having a central iron core 
surrounded by a short inner or (i primary " coil of stout wire, 
and by an outer " secondary " coil consisting of many thou- 
sand turns of very fine wire, very carefully insulated between 
its different parts. This arrangement is illustrated in Fig. 147. 

The fundamental law of induction may be thus stated : 
" Any variation or cessation of a current of electricity flowing 
in one conductor will induce a momentary current in an 
adjacent conductor ; and if the secondary conductor be an 
insulated wire coiled around the first conductor, also a coil of 
insulated wire, the effect is heightened." 

In the Ruhmkorff coil (see Fig. 148) which is an applica- 
tion of the above laws, the primary coil is of large wire and 
the secondary coil of extremely fine wire, of a length many 
thousand times greater than the wire of the primary coil. 



Note.— Fig. 149 represents an adjustable water resistance, available for 
use as an artificial load either for arc-lighting machines or the alternators. 



344 



NEW CATECHISM OF ELECTRICITY. 



Fig. 151. 




ELECTRIC LIGHT PLANT, STEAMER " BAY STATE. 



NEW CATECHISM OF ELECTRICITY. 



345 



ELECTRIC LIGHTING. 



There are two systems of electric lighting in 
common use : 

i. Arc Lighting. 

2. Incandescent Lighting. 

Candle Power, by which these are measured, 
is the amount of light given by the standard 
candle. The legal English and standard Ameri- 
can candle is a sperm candle burning "two 
grains a minute." It should have burned some FlG * 
ten minutes before use and the wick should be bent over and 
have a red tip. Otherwise its readings or indications are 
useless. A ''sixteen can die-power " lamp means a lamp 
giving the light of sixteen candles. The candle-power is a 
universal unit of illuminating power. 




Note. — According to some recent experiments made by the Govern- 
ment of the United States, a i candle-power white light is visible at a 
distance a little more than a mile, one of 3 candle-power is visible at two 
miles ; on an exceptionally clear night a white light of 3.2 candle-power 
was readily distinguished at three miles ; one of 5.6 candle-power at four 
miles, and one of 12.2 candle-power at five miles ; a green or red 2 candle- 
power light was visible at one mile, 15 candle-power at two miles, 51 
candle-power at three miles and 106 candle-power at four miles. 



346 



NEW CATECHISM OF ELECTRICITY. 



ELECTRIC LIGHTING. 

The Arc-light. — If two pointed pieces of carbon are joined 
by wires to the terminals of a generator of electric currents, 
and are brought into contact for a moment and then drawn 
apart to a short distance, a kind of electric flame called the 
arc or the voltaic arc is produced between the points of car- 
bon, and a brilliant light is emitted by the white hot points 
of the carbon electrodes. 

Th'.s phenomenon was first noticed by 
Humphrey Davy in 1800, and its explanation 
appears to be the following : Before contact 
the difference of potential between the 
points is insufficient to permit a spark to 
leap across even T oiroo" °f an i n ch of air- 
space, but when the carbons are made to 
touch, a current is established. On separat- 
ing the carbons the momentary extra-current 
due to self-induction of the circuit, which 
possesses a high electromotive-force, can 
leap the short distance, and in doing so vola- 
tilizes a small quantity of carbon between the points. Carbon 
vapor being a partial conductor allows the current to continue 
to flow across the gap, provided it be not too wide ; but as the 
carbon vapor has a very high resistance, it becomes intensely 
heated by the passage of the current, and the carbon points 
also grow hot. Since, however, solid matter is a better radiator 
than gaseous matter, the carbon points emit far more light 
than the arc itself, though they are not so hot. In the arc the 
most infusible substances, such as flint and diamond, melt ; 




Fig. 153. 



NEW CATECHISM OF ELECTRICITY. 347 

ELECTRIC LIGHTING. 

and metals such, as gold and platinum are even vaporized 
readily in its intense heat. 

When the arc is produced in the air the carbons slowly 
burn away by oxidization. It is observed, also, that particles 
of carbon are torn away from the -f- electrode, which 
becomes hollowed out to a cup- shape, and some of these 
are deposited on the — electrode, which assumes a pointed 
form. 

In the alternating current arc lamp, since the current 
flows alternately in each direction, the carbons burn away 
with uniform rapidity and the ends assume about the same 
form. The light will be thrown up and then down as the di- 
rection of the current changes, and for this reason reflectors 
are placed above the arc to catch the upward rays. 

The familiar prism and spectrum experiment shows that 
all ordinary "white" light is made up of colors, shades of 
red, yellow, green and blue. The quality of any light will 
depend upon both the presence and intensity of these com- 
ponent color-groups. When the incandescent lamp burns 
low the red and yellow rays are mainly present ; as it grows 
hotter the greens and blues are added, until, when all are 
present in correct proportion, the light is pure white. Analy- 
sis of the components of ordinary lights shows that the 
candle and oil flames are made up mainly of red and yellow, 
with some green and faint blue rays. 

The two pencils in the modern arc lamp are separated by 
a distance of from one-sixteenth to three-sixteenths of an 



343 



NEW CATECHISM OF ELECTRICITY. 



Fig. 154. 



Fig. 155. 



RHEOSTAT. 
Fig. 156. 




double; knife; switch. 



single; kniee; switch. 

inch. The electricity, in 
overcoming the resistance 
of this air gap, generates 
such an amount of heat that 
the tips are kept at a white 
glow. The carbon toward 
the positive pole of the 
machine will be found to be 
cone-shaped with a depress- 
ion at the top, whence it 
derived the name " arc- 
light " — the crater in the 
cone assuming the form ( 



NEW CATECHISM OF ELECTRICITY. 349 

ELECTRIC LIGHTING. 

an arc or part of a circle. The other carbon will be found 
slightly rounded with a little pyramid just beneath the crater 
of the upper carbons. Under these conditions, it will be 
noticed that the positive carbon, or one nearest the positive 
brush of the dynamo, will burn away much faster than the 
other, and because the greater amount of light is desired 
below the lamp, the positive carbon is placed above the other. 

Long before the incandescent electric light had been in- 
vented, the arc light made by an electric arc formed between 



* Note. — It was about this time that popular explanations begun to 
be made of the nature and source of electricity ; on the installation of a 
4,000 candle light arc lamp, one man who had gathered a crowd around 
him thus proclaimed, calling attention to the solenoid at the top of the 
lamp : " That is the can that holds the oil," and, speaking of the side rod 
of the lamp, " That is the tube which conducts the oil from the can to the 
burner." This season also witnessed the introduction of the arc light 
into ' ' Wannamaker's " at Philadelphia. One gentleman on that occasion 
looked the whole apparatus over very carefully, perhaps a half hour, 
sized it up, and then, pointing to the line wire, he said, " How large is 
the hole in that wire that the electricity flows through ? " Another 
gentleman, one connected with a great manufacturing company, observed 
in complete silence the machine running for perhaps five minutes. Then 
he fully digested the whole thing, and was ready to tell all about it. He 
said, "The electricity in that thing is generated by that revolving busi- 
ness there, rubbing the air up against these iron blades (meaning the 
magnets;, just as you get sparks when you rub a cat's back." 

In the following year, 1879, the Cincinnati Exposition Buildings were 
lighted, and an expert from New York City was sent out to make matters 
go smooth, but one distressful night he failed to appear, and a self-exam- 
ined engineer was put in charge, but the lamps would not "illumine " — 
so the next morning Mike was sent for. "Well, Mike, why didn't your 
light burn last night? " " Sure, sir, I don't know. I do be thrying to do 
me part ; it's more than the full of a box of matches I spint a-thrying to 
light thim two bla^k sticks, and dev'l a light could I get." The great pile 
of burnt matches under the lamp bore evidence of the truth of Mike's 
assertion. 



350 



NEW CATECHISM OF ELECTRICITY. 



Fig. 157. 



Fig. 158. 





LAMP SOCKETS. 
Fig. 159. 




SWITCH BOARD. 



NEW CATECHISM OF ELECTRICITY. 351 



ELECTRIC LIGHTING. 

the ends of two carbon pencils, was used for illuminating 
purposes. At first a dynamo was used to run a single light, 
but, in the year 1878, Mr. Chas. F. Brush invented and devel- 
oped the modern series arc lamp with the shunt coil, which 
may justly be considered the birth of the electric lighting 
industry of the world. 

It is worthy of permanent record, as stated by Mr. Foree 
Bain, that "in 1879 the Maxim Electric I^ight Company of 
New York took the contract to light the exposition building 
in Cincinnati with arc lights. The plant consisted of ten 
twenty-thousand candle power lamps and ten separate dyna- 
mos for these lamps, and seven ten-thousand candle power 
lamps and seven corresponding dynamos, that is, a dynamo 
for each lamp. 

" The dynamos were of the gramme ring type, with 
wrought-iron field magnets, stationary brush holders. The 
lamps were made almost entirely of brass, and were beautiful 
in design and finish, but they required new adjustment with 
each change of the current value. 

" The dynamos were marked 15 webbers. 

" The circuit consisted of copper wire on one side, and gas 
pipes on the other side, when they were available. The cop- 
per wire was plain and uncovered, and was procured of the 
tinners and hardware stores. 

" All of the dynamos and all of the lamps were connected 
in parallel between the outgoing conductors and the gas 



352 



NEW CATECHISM OF ELECTRICITY. 



ELECTRIC LIGHTING. 

Fig. 160. 




To Fit Thomson-Houston Socket. 
INCANDESCENT LAMPS. 



NEW CATECHISM OF ELECTRICITY. 353 

ELECTRIC LIGHTING. 

pipes. It is true the gas pipes did get quite warm, but I 
thought that that was an indication that the business was 
working well. 

" In this plant I didn't have a socket, a switch, a piece cf 
insulated wire, a fuse, an automatic cut-out, a switchboard, a 
ground detector, a voltmeter, an ammeter, nor an inspector's 
certificate. Yet the plant ran for thirty nights without a 
' hitch.'" 

The light of the arc lamp approaches nearest to that of 
sunlight ajf any of the artificial lights used. It is used not 
only for the general purposes of illumination but also exten- 
sively in photography. The arc light per candle power is 
much cheaper than the incandescent light, but up to the 
present time the arc lamp has not been successfully made in 
as small units. 

In the field of electric lighting, there is a much greater 
chance for extraordinary improvements than in that of the 
application of power. In an "arc" light, less than ten per 
cent, of the energy applied is converted into light ; the 
balance passes off in the form of heat. In incandescent lights 
the efficiency is still lower, being about four or five per cent. 

Incandescent Lighting. — The device, with the arc light, 
has, more than any other, introduced electricity as an in- 
dustrial agent to public approval is the incandescent lamp. 

From the time of the perfection of the now familiar pear- 
shaped globe, with its thread-like strip of carbon, capital has 



354 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC LIGHTING. 

freely flowed forth from its strong vaults to the accomplish- 
ment of thousands of projects for the utilization of the electric 
force. It has been an illustration of the proverb that ' i seeing 
is belie ving." 

The history of the development of the incandescent lamp 
is one of the most interesting to be found in the literature of 
inventions. Its successful accomplishment was akin to the 
taming a wild horse to docile service. The first strictly 
incandescent lamp was invented by de Molyens of Chelten- 
ham, England, in 1841 ; its foundation principle was the pro- 
duction of a white light by the high resistance of a platinum 
wire to the passage of the electric current ; in 1845 J. W. 
Starr of Cincinnati first proposed the use of carbon. Experi- 
ments soon demonstrated the great advantages of the carbon 
over the platinum or any other metal. 

Many different forms of incandescent lamps have been 
made, but all are nearly of the same principle of construction,, 
making use of the carbon filament. In 1880 Edison patented 
the lamp of which millions have been put into use. The 
manufacture of incandescent lamps has developed into en- 
ormous proportions owing to the fact that the value of the 
entire device is destroyed the instant the slender filament is 
broken — it is here as in many other manufactured articles,, 
"the weakness of the goods is the strength of the trade." 

Lamp Circuits. — An electric pressure being available, it is 
necessary, in order to have an electric flow, to provide a con- 
tinuous conducting path from the point of positive potential 






NEW CATECHISM OF ELECTRICITY. 355 

ELECTRIC LIGHTING. 

to the point of negative potential. This path, whether com- 
posed simply of wires, or of lamps, motors, or other applica- 
tions of electric power is called a circuit, and circuits may be 
divided into two kinds, viz.: series circuits, and parallel or 
shunt circuits. In the series circuit (Fig. 161), the wires, lamps, 
etc. , are arranged end to end, so as to form one continuous 
conducting path connecting the two points of higher and 
lower potential, and the current in flowing between these 
points passes in succession through each of the lamps or other 
appliances composing the circuit. In the parallel or shunt 
circuit (Fig. 162), two main wires or leads M x M 3 are connected 
to the points of higher and lower potential, and the lamps, 
wires, etc., are connected across the two mains, or arranged 
side by side so as to form a number of independent paths or 
branches, and the current, in flowing from the higher to the 
lower potential, divides itself amongst these branches in in- 
verse proportion to their resistance. It will be apparent that 
the total resistance of the parallel arrangement is less than 
that of any of its branches, for these, being arranged side by 
side, are equivalent to one having a cross section equal to the 
cross section of the branches. If the resistances of all the 
branches are equal, the total resistance of the circuit will be 
equal to the resistance of one branch divided by the number 
of branches. 

The total resistance of the series circuit is evidently equal 
to the sum of the resistances of each of its separate parts, 
since these are included in one continuous path ; and, for 
the same reason, the strength of the current flowing in a 



356 NEW CATECHISM OF ELECTRICITY. 



ELECTRIC LIGHTING. 



Fig. 161. 



+•— © — -€> — ©■ 



-•— (9 — © — & 




SERIES CIRCUIT. 



Fig. 162. 



+va 




PARAIvWL, CIRCUIT. 



NEW CATECHISM OF ELECTRICITY. 357 

ELECTRIC LIGHTING. 

series circuit is obviously everywhere the same. A circuit 
is said to be " closed " when it forms a continuous conducting 
path, and to be ' ' open ' ' when a discontinuity occurs in some 
portion such that an electric current cannot flow. When a 
circuit is connected or bridged across in such a manner, by 
some conducting material, so as to offer a resistance less than 
its normal working resistance, it is said to be cross-circuited 
or short-circuited. 

Systems of Distribution. — The several methods for arrang- 
ing the distribution of the electric current may be thus classi- 
fied : 

1. The multiple arc system. 

2. The multiple series system. 

3. The three- wire system. 

4. The alternating transformer system. 

The multiple arc system is illustrated in Fig. 163, which 
will readily show the method of distribution. This is also 
called the parallel system. 

The multiple series system is represented in Fig. 164. This 
is a combination of the series with the parallel systems ; that 
is, several series in parallel with each other. 

The three-wire system is also illustrated in Fig. 164, where 
A A represent two dynamos, which are connected in such a 
manner that, while the total voltage of the system is 220, the 
lamps being connected to a third or neutral wire receive only 



358 



NEW CATECHISM OF ELECTRICITY. 



ELECTRIC LIGHTING. 

Fig. 163. 





V V V V \ v \ *' 




®« 



TWO WIRE INCANDESCENT SYSTEM. 
Fig. 164. 




ZEUL 



"«- 



TTTTT 



THREE) WIRE INCANDESCENT SYSTEM. 
FiG. 165. 



g?*" 



1**4 i 



i M 4 I 



ALTERNATING SYSTEM. 






NEW CATECHISM OF ELECTRICITY. 359 

ELECTRIC LIGHTING. 

1 10. By this means the voltage is doubled and the cost of 
copper accordingly reduced to one-fourth, or, practically, 
taking the central wire into consideration, to not more than 
three-eighths. 

The alternating transformer system is shown in Fig. 165. 
The transformer or converter in the circuit is represented by 
the two letters C C. 

In the alternating current system, for distribution in the 
open air, a high potential current is used, from 1,000 to 10,000 
volts being maintained at the central station ; two leads un- 
connected at the end lead from the station. Where current is 
desired, a converter is placed, whose primary is connected to 
the two leads, bridging the interval between them. From the 
secondary the house leads are taken with alow induced initial 
potential, in some cases of 50 volts. By the insurance rules, 
the converters are kept outside of buildings. 

The Switchboard. — With the exception of the automatic 
regulation of the generator, there is nothing so important in 
stations operating arc lights, as the switchboard. In Fig. 159 
is shown the arc plug switchboard, by the use of which any 
combinations either of circuits or machines are easily effected 
without danger of personal injury to the operator, or of dis- 
turbing or extinguishing the lights. 



Note. — Edison's discovery of the high resistance filiment solved the 
problem and made it possible to use a voltage of about 1 10 for distributing 
purposes. Even this was found inadequate for large areas, and he after- 
wards devised the three-wire system. 



360 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC LIGHTING. 

The Electric Lamp of the Future, — Neither of the two 
forms of lamp now in common use for electric lighting yields 
all the results that could be desired. The arc concentrates 
the illumination too much ; the incandescent burner, while 
sub-dividing it, is wasteful of energy. It develops heat, and 
this is a net loss. The phosphorescent lamp at present re- 
quires current of too high potential and frequency of altera- 
tion to be economical. The arc lamp is yet to be touched up 
to more perfectly uniform action ; the glow lamp is to be 
cheapened. 

Vacuum Tube Electric Lamps. — Partial vacuum tubes 
known as Geisler's and Crooke's have been in use for years 
as a source of light in which, as is generally known, the light 
is produced by the passage of the electric discharge through 
the rarefied gas of the tube. In such light there is no com- 
bustion and only very little heat. 

Tubes five or Six feet long, three or four inches in diam- 
eter, and of any shape, may be lighted, and shine with a 
bluish white light, vastly brighter than any have been lighted 
before. The electric terminals for these tubes are not wires 
sealed into them, but metallic caps upon their ends. These 
act inductively upon and through the residual air contained in 
the hermetically sealed tube. 

This form of lighting has been attempted before, but the 
results for practical purposes have not been satisfactory. The 
light has not been obtained in sufficient quantity, and the 
apparatus necessary for producing it has been expensive and 



NEW CATECHISM OF ELECTRICITY. 



361 



ELECTRIC LIGHTING. 

somewhat complicated, and the current employed difficult to 
insulate. The apparatus has now been greatly simplified and 
an unusual volume of light obtained from the tubes, while the 
current employed is under comparatively low potential. 

A Geisler Tube is a glass tube containing two platinum 
wire terminals passing through the glass and having the air 
exhausted so as to leave a partial vacuum. Electric dis- 
charges or sparks pass between the two wires much more 
easily in a vacuum than in ordinary air. The passage of the 

Fig. 166. 




Type 1 



3 4 5 G 

GEISI,KR TUBKS. 



€ 



discharge causes the air or other gas to become dimly lumin- 
ous. The color of the light depends upon the kind of glass 
and upon the gas enclosed. Geisler tubes are sometimes 
made in beautiful designs. The incandescent lamp is the 
most common form of the Geisler tube. 



362 NEW CATECHISM OF ELECTRICITY. 

ELECTRIC LIGHTING. 

Crooke' } s Tube f or Crooke's Radiometer. — This is a device 
similar to the f< Geisler " tube and produces the most power- 
ful rays known to physicists. 

The rays, however, do not come from the visible illumina- 
tion. Prof. Roentgen calls them X rays, for want of any 
other name. They cannot be seen. They are mysterious and 
unknown, except that they are proven to exist. 

The remarkable property of the X rays is the power to 
penetrate objects opaque to the human eye, as a block of 
wood, the human body and thousands of other things. The 
rays falling upon an opaque object do not render it translu- 
cent in the sense that the eye can then see within or beyond 
it. The manner in which it is proved that the rays penetrate 
the opaque object is to make a photograph of the interior of 
the object. 

It is quite a different process from ordinary photography. 
The object to be photographed, a lead pencil for instance, is 
placed between the Roentgen light and a sensitized plate. 
The X rays penetrate the wood and whiten the plate. They 
fail to penetrate the lead within the wood, and that is shown 
in black relief upon the plate. So with the hand. The hand 
is put between the light and the plate. The X rays pass 
through the flesh and whiten the plate, but the rays cannot 
penetrate the bones, so the bones are shown in black shadow 
on the plate. 

Standard Incandescent Lamp Sockets. — This is a question 
for immediate agreement among makers. It is thought the 



NEW CATECHISM OF ELECTRICITY. 



3^3 



ELECTRIC LIGHTING. 

most practical and satisfactory solution is a form of base or 
mount so inexpensive that when the lamp is destroyed the 
base may be allowed to go with it as in itself a thing of no 
value. In view of the fact that high tension lamps are in all 
probability to be the lamp of the future, the question of a safe 
socket acquires vast importance. Porcelain will no doubt 
come largely into use for this purpose, which will greatly 
modify the conditions governing the selection of both a base 
and socket. See Figs. 157, 158, 160. 




ORNAM3NTAI, LAMP. 



364 NEW CATECHISM OF ELECTRICITY. 




MODKL. ELECTRIC LIGHTING DYNAMO. 



NEW CATECHISM OF ELECTRICITY. 



365 




Whatever the source of electrical energy and whatever 
devices may be used to convert it into its destined purpose 
the transference is made by the means of wire. 

Gas, water, etc., are distributed for all sorts of purposes 
and the laws governing them are similar to those governing 
electricity. Bach trade has, of course, some elements which 
have to be considered that are neglected in others, but the 
main laws are common to all and do not require different 
interpretations except possibly in degree. 



Note. Size for size, a thread of spider silk, it is said, is decidedly 
tougher than a bar of steel. An ordinary thread will bear a weight of 
three grains. This is just about fifty per cent, stronger than a steel 
thread of the same thickness. 



366 NEW CATECHISM OF ELECTRICITY. 

WIRING. 

A habit of studying the distribution of electricity as is done 
with the distribution of steam, gas, water, etc., soon make all 
the problems easy to understand. 

The use of wire has been traced back to the earliest Egypt- 
ian history. Specimens are in existence which can be proven 
to date to 1700 B. C. Kensington Museum has a specimen 
which was made in Minera, 800 years B. C. Ancient literature 
contains many references to wire. From the ruins of Hercu- 
laneum metal heads have been exhumed on which the hair is 
represented by wire. 

There is no question that this ancient wire was made by 
hammering out the metal, which was always bronze or of the 
precious group. This held true of all made previous to the 
fourteenth century, during which the process of forming wire 
by drawing or elongating the metal by forcing it through a 
conical orifice, made in some substance harder than the metal 
treated, was invented. 

The subject naturally divides itself into : 

Klectric bell wiring, including fire and burglar alarms. 
Wiring for incandescent, or glow, lamps. 

3. Wiring for arc lights. 

4. Wiring for telephones and telegraphs. 
Wiring for railway and power plants, including over- 
head wiring, car wiring, and station wiring. 

A good wiring installation should have the following attri- 
butes ; 



NEW CATECHISM OF ELECTRICITY. 



367 



Fig 161. 



WIRING. 

First, it should supply the lamps with current, 
and provide appropriate means of controlling che 
lights. 

Second, the current should be distributed to 
the lamps at a constant pressure. That is, the 
voltage of the dynamo being constant, and also 
the n amber of lamps, the voltage from socket to 
socket should not vary beyond a certain amount. 
Third, the wiring should comply with the 
insurance rules in force in the locality in which 
the work is done. 

Fourth, a minimum amount of copper should 
be used in the accomplishment of the result. 
wire;. Prof. S. P. Thompson says what is wanted is 

a mode of running- the wires and fixing the 
switches and other accessories, that they shall not only be 
electrictight, but shall be watertight, gastight, airtight, oil- 
tight and rattight, 



Fig. 162. 




and he adds that 
all of the above 
requirements; and 
more, are filled by 
a properly insulat- 
ed conductor in- 
closed in an injury- 
resisting metal 
pipe. 



Fig. 163. 



5 



PORCELAIN ROSETTE. 



e 



BINDING 
POST. 



368 



NEW CATECHISM OF ELECTRICITY. 



WIRING. 




List of Tools useful for small inside wiring : 
Corner Brace as shown in Fig. 164. 
Several sizes of small Bits. 

I2 7/ and 24 7/ Twist Point Bell Hangers. 
Gimlet for */*" hole. 
Metre Box. 

Combination Handle with set of small tools. 
Rat Tail File. 

Small Screw Driver. 
Flat Chisel. 

Medium Size Hammer. 
Key-hole Saw. 



NEW CATECHISM OF ELECTRICITY. 369 



FUSES. 



Fuse wire is a safety device designed to break the electric 
circuit when an excessive current passes, and it breaks the 
circuit because it is heated to a point at which it melts. 

Other designations are " Safety Cutouts," l ' Safety Fuses, ' ' 
" Fuse Blocks" and " Safety Catches." 

The main object of fuses is a protection against fire, as the 
fuse melts at such a low temperature that it will not set lire to 
inflammable material. If a short circuit was to occur on a cir- 
cuit unprotected by fuse the copper would become red hot and 
finally melt, and if in contact with wood or other combustible 
material, or should the melted copper fall on anything inflam- 
mable it would be cause of a fire. 

Fuses should be placed wherever the size of wire changes 
or wherever there is a branch of smaller size wire connected, 
unless the next fust on the main or larger wire is small 
enough to protect the branch or small wire, but more lights 
may be added on the large wire, making it necessary to put in 
a larger. 

The illustrations on page 370 show the different forms and 
patterns of the device. 



37o 



NEW CATECHISM OF ELECTRICITY. 



SAFETY FUSES. 



Fig. 165. 



Fig. 166. 



Fig. 167. 



Fig. 168. 








Fig. 169. 



NEW CATECHISM OF ELECTRICITY. 37 l 



SAFETY FUSES. 

" Points ' ' relating to the Safety Fuse. 
Covered fuses are more sensitive than open ones. 
A fuse wire should be rated for its carrying capacity for the 
ordinary lengths employed. 

On important circuits fuses should be frequently renewed. 

Fuses up to five amperas should be at least ?.% ins. long, 
Y2 m. to be added for each increment of five amperes capacity. 

Round fuse wires should not be employed in excess of 
thirty amperes capacity. For higher currents flat ribbons of 
lour inches and upwards should be used. 

Experiments have shown that for large fuses, a multiple 
fuse is more sensitive than a single one. A one hundred 
ampere fuse may be made by taking four wires of twenty-five 
amperes capacity. 

Unless a fuse be long and quite heavy, its carrying capacity 
is practically the same whether it be placed vertically or hori- 
zontally. 

Experience seems to show that the best alloy for a fuse is 
one of lead and tin, the lead being considerably in excess. If 
too much lead is used, the fuses deteriorate rapidly and coat 
with the white film. 

A fuse block may be overloaded, not because the metal of 
the terminals is not of sufficient cross-section to carry the 
current, but because of insufficient area of, or loose contact of, 
fuse, or wires, and this heating is very frequently the cause of 
fuses melting. 



372 NEW CATECHISM OF ELECTRICITY. 



SAFETY FUSES. 

Wires and fuses should be screwed up tight, as it is fre- 
quently the case the area of contact of wires or fuse is not 
sufficient to prevent heating when there is a full load on the 
wires. 

The area of contact should be several times the cross- 
section of the wires connected and for that reason, in the case 
of large size wires, the ends should be flattened if connected 
under the head of a binding screw. 

A leading question now is the automatic circuit breaker 
versus the fuse wire. Both these devices are excellent in 
themselves, but each requires judgment in selection and use. 
The automatic circuit breaker is to be preferred for switch 
board use and motor service. A circuit breaker placed in plain 
sight on the front of the board is to be preferred in all cases. 

For lighting circuits, it is doubtful if any simpler and bet- 
ter device than the fuse wire can be used. In spite of all that 
has been said against it, when properly used and taken care 
of, it leaves little or nothing to be desired ; yet there is noth- 
ing about the plant that is more dangerous when ignorantly 
or carelessly used. 



NEW CATECHISM OF ELECTRICITY. 373 



IMPORTANT. 



The National Code is said to be the wiremen's Bible ; it 
says "Thou shalt not use this, and thou shalt not do that/' 
and it also contains for him who will study it, the principles 
which enable him to decide what he ought to do. 

The code is not intended to be a cast-iron set of regulations 
or a complete specification of how to do construction, but it is 
designed to serve as the common law of electrical construction, 
to indicate what things must always be done, what must never 
be done, and to set forth the principles which should be 
observed in order to secure safety. It is the spirit of the code, 
even more than the letter, that should be studied by the archi- 
tect and the engineer. 

It is impossible to conceive a set of regulations which 
would describe all the necessary requirements of good work, 
but an observance of the principles underlying these rules will 
enable us to determine what material and construction is suit- 
able and what is best for each particular case. 



374 NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

National Board Pire Underwriters. 



RULES AND REQUIREHENTS 

Of the National Board of Fire Underwriters for the 
Installation of Wiring and Apparatus for Electric 
Light and Power as Recommended by the Under- 
writers' and National Electric Association. 

The use of wire ways for rendering concealed wiring 
permanently accessible is most heartily endorsed and recom- 
mended ; and this method of accessible concealed construction 
is advised for general use. 

Architects are urged, when drawing plans and specifica- 
tions, to make provisions for the channeling and pocketing 
of buildings for electric light or power wires, and in specifica- 
tions for electric gas lighting to require a two-wire circuit, 
whether the building is to be wired for electric lighting or not, 
so that no part of the gas fixtures or gas piping be allowed to 
be used for the gas lighting circuit. 

Class A. Central Stations for Light or Power. 

These Rules also apply to Dynamo Rooms in Isolated 
Plants, connected with or detached from buildings used for 
other purposes ; also to all varieties of apparatus therein of 
both high and low potential. 



New catechism of electricity. 375 

WIRING RULES AND REQUIREMENTS. 

1. Generators : 

a. Must be located in a dry place. 

b. Must be insulated on floors or base frames, which 
must be kept filled, to prevent absorption of moisture, and 
also kept clean and dry. 

c. Must never be placed in a room where any hazardous 
process is carried on, nor in places where they would be 
exposed to inflammable gases, or flyings of combustible 
material. 

d. Must each be provided with a waterproof covering. 

2. Care and Attendance : 

A competent man must be kept on duty in the room 
where generators are operating. 

Oily waste must be kept in approved metal cans and 
removed daily. 

3. Conductors : 

From generators, switchboards, rheostats or other 
instruments, and thence to outside lines, conductors — 

a. Must be in plain sight and readily accessible. 

b. Must be wholly on non-combustible insulators, such 
as glass or porcelain. 

c. Must be separated from contact with floors, partitions 
or walls through which they may pass, by non-combustible 
insulating tubes, such as glass or porcelain. 

d. Must be kept rigidly so far apart that they cannot 
come in contact. 

e. Must be covered with non-inflammable insulating 
material sufficient to prevent accidental contact, except that 
(s bus bars " may be made of bare metal. 



376 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

f. Must have ample carrying capacity, to prevent heat- 
ing. (See Capacity of Wires Table.) 

4. Switchboards : 

a. Must be so placed as to reduce to a minimum the 
danger of communicating fire to adjacent combustible 
material. 

b. Must be accessible from all sides when the connections 
are on the back ; or may be placed against a brick or stone 
wall when the wiring is entirely on the face. 

c. Must be kept free from moisture. 

d. Must be made of non-combustible material, or of hard 
wood in skeleton form, filled to prevent absorption of moisture. 

e. Bus bars must be equipped in accordance with Rule 3 
for placing conductors. 

5. Resistance Boxes and Equalizers : 

a. Must be equipped with metal, or other non-com- 
bustible frames. (See Definitions.) 

b. Must be placed on the switchboard, or, if not thereon, 
at a distance of a foot from combustible material, or separated 
therefrom by a non-inflammable, non-absorptive, insulating 
material. 

6. Lightning Arresters : 

a. Must be attached to each side of every overhead 
circuit connected with the station. 

b. Must be mounted on non-combustible bases in plain 
sight on the switchboard, or in any eqtially accessible place, 
away from combustible material. 



NEW CATECHISM OF ELECTRICITY. 377 

WIRING RULES AND REQUIREMENTS. 

c. Must be connected with at least two " earths " by 
separate wires, not smaller than No. 6 B. & S., which must 
not be connected to any pipe within the building, and must 
be run as nearly as possible in a straight line from the 
arresters to the earth connection. 

d. Must be so constructed as not to maintain an arc after 
the discharge has passed. 

7. Testing : 

a. All series and alternating circuits must be tested 
every two hours while in operation, to discover any leakage 
to earth, abnormal in view of the potential and method of 
operation. 

b. All multiple arc low potential systems (300 volts or 
less) must be provided with an indicating or detecting device, 
readily attachable, to afford easy means of testing where the 
station operates continuously. 

c. Data obtained from all tests must be preserved for 
examination by insurance inspectors. 

These rules on testing to be applied at such places as may 
be designated by the association having jurisdiction. 

8. Motors : 

a. Must be wired under the same precautions as with a 
current of the same volume and potential for lighting. The 
motor and resistance box must be protected by a double pole 
cut-out and controlled by a double-pole switch, except in 
cases where one- quarter horse-power or less is used on low 
tension circuit, a single pole switch will be accepted. 



37$ NEW CATECHISM OF ELECTRICITY. 



NATIONAL BOARD FIRE UNDERWRITERS. 

b. Must be thoroughly insulated, mounted on filled dry 
wood, be raised at least eight inches above the surrounding 
floor, be provided with pans to prevent oil from soaking into 
the floor, and must be kept clean. 

c. Must be covered with a waterproof cover when not in 
use, and, if deemed necessary by the Inspector, be inclosed in 
an approved case. (See Definitions.) 

9. Resistance Boxes : 

a. Must be equipped with metal or other non-com- 
bustible frames. (See Definitions.) 

b. Must be placed on the switchboard, or at a distance 
of a foot from combustible material, or separated therefrom 
by a non-inflammable, non-absorptive, insulating material. 

Class B. High Potential Systems, over 300 Volts. 

Any circuit attached to any machine, or combination of 
machines, which develop over 300 volts difference of potential 
between any two wires, shall be considered as a high potential 
circuit and coming under that class, unless an approved trans- 
forming device is used, which cuts the difference of potential 
down to less than 300 volts. 

10. Outside Conductors — Ali, Outside, Overhead Con- 

ductors (Including Services) : 

- a. Must be covered with some approved insulating 
material, not easily abraded, firmly secured to properly 
insulated and substantially built supports, all tie wires having 
an insulation equal to that of the conductors they confine, 
(See Definitions.) 



NEW CATECHISM OF ELECTRICITY. 



379 



Fig. 170. 




MICROMETER WIRE GUAGE. 



3 SO NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

b. Must be so placed that moisture cannot form a cross 
connection between them, not less than a foot apart, and not 
in contact with any substance other than their insulating 
supports. 

c. Must be at least seven feet above the highest point of 
flat roofs, and at least one foot above the ridge of pitched 
roofs over which they pass or to which they are attached. 

d. Must be protected by dead insulated guard irons or 
wires from possibility of contact with other conducting wires 
or substances to which current may leak. Special precautions 
of this kind must be taken where sharp angles occur, or where 
any wires might possibly come in contact ^ 'th electric light 
or power wires. 

e. Must be provided with petticoat insulators of glass or 
porcelain. Porcelain knobs or cleats and rubber hooks will 
not be approved. 

f. Must be so spliced or j oined as to be both mechanically 
and electrically secure without solder. The joints must then 
be soldered, to insure preservation, and covered with an insula- 
tion equal to that on the conductors. (See Definitions. ) 

g. Telegraph, telephone and similar wires must not be 
placed on the same cross-arm with electric light or power 
wires. 

ii. Service Blocks : 

Must be covered over their entire surface with at least 
two coats of waterproof paint. 

12. All Interior Conductors : 

a. Must be covered where they enter buildings from 
outside terminal insulators to and through the walls, with 



NEW CATECHISM OF ELECTRICITY. 38 1 

NATIONAL BOARD FIRE UNDERWRITERS. 

extra waterproof insulation, and must have drip loops outside. 
The hole through which the conductor passes must be bushed 
with waterproof and non-combustible insulating tube, slanting 
upward toward the inside. The tube must be sealed with 
tape, thoroughly painted, and securing the tube to the wire. 

b. Must be arranged to enter and leave the building 
through a double contact service switch, which will effectually 
close the main circuit aud disconnect the interior wires when 
it is turned ' ' off. ' ' The switch must be so constructed that 
it shall be automatic in its action, not stopping between points 
when started, and prevent an arc between the points under all 
circumstances ; it must indicate on inspection whether the 
current be"on" or " off," and be mounted in a non-com- 
bustible case, and kept free from moisture, and easy of access 
to police or firemen. So-called " snap switches" shall not 
be used on high potential circuits. 

c. Must be always in plain sight, and never encased, 
except when required by the Inspector. 

d. Mus'; be covered in all cases with an approved non- 
combustible material that will adhere to the wire, not fray by 
friction, and bear a temperature of 150 F. without softening. 
(See Definitions.) 

e. Must be supported on glass or porcelain insulators, 
and kept rigidly at least eight inches from each other, except 
within the structure of lamps or on hanger-boards, cut-out 
boxes, or the like, where less distance is necessary. 

f. Must be separated from conctact with walls, floors, 
timbers or partitions through which they may pass by non- 
combustible insulating tube. 



382 . NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

g. Must be so spliced or joined as to be both 
mechanically and electrically secure without solder. They 
must then be soldered, to insure preservation, and covered 
with an insulation equal to that on the conductors. 

13. Arc L/Amps — In Every Case : 

a. Must be carefully isolated from inflammable material. 

b. Must be provided at all times with a glass globe 
surrounding the arc, securely fastened upon a closed base. 
No broken or cracked globes to be used. 

c. Must be provided with an approved hand-switch, also 
an automatic switch, that will shunt the current around the 
carbons should they fail to feed properly. (See Definitions. ) 

d. Must be provided with reliable stops to prevent 
carbons from falling out in case the clamps become loose. 

e. Must be carefully insulated from the circuit in all 
their exposed parts. 

f. Must be provided with a wire netting around the 
globe, and an approved spark arrester above to prevent escape 
of sparks, melted copper, or carbon, where readily inflammable 
material is in the vicinity of the lamps. It is recommended 
that plain carbons, not copper-plated, be used for lamps in 
such places. (See Definitions.) 

g. Hanger-boards must be so constructed that all wires 
and current-carrying devices thereon shall be exposed to view 
and thoroughly insulated by being mounted on a waterproof 
non-combustible substance. All switches attached to the same 
must be so constructed that they shall be automatic in their 
action, not stopping between points when started, and pre- 
venting an arc between points under all circumstances. 



NEW CATECHISM OF ELECTRICITY. 383 

NATIONAL BOARD FIRE UNDERWRITERS. 

h. Where hanger boards are not used, lamps to be hung 
from insulated supports other than their conductors. 

14. Incandescent l,amps in Series Circuits having a 

Maximum Potential oe 300 Volts or over : 

a. Must be governed by the same rules as for arc lights, 
and each series lamp provided with an approved hand spring 
switch and automatic cut-out. 

b. Must have each lamp suspended from a hanger-board 
by means of a rigid tube. 

c. No electro-magnetic device for switches and no system 
of multiple series or series multiple lighting will be approved. 

d. Under no circumstances can series lamps be attached 
to gas fixtures. 

Class C. Low Potential Systems, 300 Volts or less. 

15. Outside Overhead Conductors : 

a. Must be erected in accordance with the rules for high 
potential conductors. 

b. Must be separated not less than 12 inches, and be 
provided with an approved fusible cut-out, that will cut off 
the entire current as near as possible to the entrance to the 
building and inside the walls (See Definitions.) 

16. Underground Conductors : 

a. Must be protected against moisture and mechanical 
injury, and be removed at least two feet from combustible 
material when brought into a building, but not connected 
with the interior conductors. 



384 NEW CATECHISM OF ELECTRICITY. 



WIRING RULES AND REQUIREMENTS. 

b. Must have a switch and a cut-out for each wire 
between the underground conducters and the interior wiring 
when the two parts of the wiring are connected. 

These switches and fuses must be placed as near as 
possible to the end of the underground conduit, and connected 
therewith by specially insulated conductors, kept apart not 
less than two and one-half inches. (See Definitions.) 

c. Must not be so arranged as to shunt the current 
through a building around any catch -box. 

17. Inside Wiring— General Rules : 

At the entrance of every building there shall be an 
approved switch placed in the service conductors by which 
the current may be entirely cut off. (See Definitions.) 

18.. Conductors : 

a. Must have an approved insulating covering, and must 
not be of sizes smaller than No. 14 B. & S., No. 16 B. W. G., 
or No. 4 B. S. G., except that in conduit installed under Rule 
22, No. 16 B. & S., No. 18 B. W. G., or No. 4 B. S. G. may be 
used. (See Definitions.) 

b. Must be protected when passing through floors ; or 
through walls, partitions, timbers, etc., in places liable to be 
exposed to dampness by waterproof, non-combustible, 
insulating tubes, such as glass or porcelain. 

Must be protected when passing through walls, partitions, 
timbers, etc., in places not liable to be exposed to dampness 
by approved insulating bushings specially made for the 
purpose. (See Definitions.) 



NEW CATECHISM OF ELECTRICITY. 



385 



Fig. 171. 




^^JLiLil 



BIRMINGHAM WIRE GUAGE) (B. W, G, ) 



386 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

c. Must be kept free from contact with gas, water or 
other metallic piping, or any other conductors or conducting 
material which they may cross (except high potential conduc- 
tors) by some continuous and firmly fixed non-conductor- 
creating a separation of at least one inch. Deviations fromi 
this rule may sometimes be allowed by special permission.. 

d. Must be so placed in crossing high potential conduc- 
tors that there shall be a space of at least one foot at all points* 
between the high and low tension conductors. 

<?. Must be so placed in wet places that an air space will 
be left between conductors and pipes in crossing, and the 
former must be run in such a way that they cannot come in 
contact with the pipe accidentally. Wires should be run over 
all pipes upon which condensed moisture is likely to 
gather, or which by leaking might cause ^trouble on a circuit. 

f. Must be so spliced or joined as to be both mechanically 
and electrically secure without solder. They must then be 
soldered, to insure preservation, and covered with an insula- 
tion equal to that on the conductors. (See Definitions.); 



Special Rules. 

19. Wiring not Encased in Moulding or Approved 
Conduit: 
a. Must be supported wholly on non-combustible 
insulators, constructed so as to prevent the insulating cover- 
ings of the wire from coming in contact with other substances 
than the insulating supports.. 



NEW CATECHISM OF ELECTRICITY. 3^7 

WIRING RULES AND REQUIREMENTS. 

b. Must be so arranged that wires of opposite polarity, 
with a difference of potential of 150 volts or less, will be kept 
apart at least two and one-half inches. 

c. Must have the above distance increased propor- 
tionately where a higher voltage is used. 

d. Must not be laid in plaster, cement or similar finish. 

e. Must never be fastened with staples. 

In Unfinished Lofts between Floor and Ceilings, 
in Partitions and other concealed Places. 

f. Must have at least one inch clear air space surround- 
ing them. 

g. Must be at least ten inches apart when possible, and 
should be run singly on separate timbers or studding. 

h. Wires run as above immediately under roofs, in 
proximity to water-tanks or pipes, will be considered as 
exposed to moisture. 

i. When from the nature of the case it is impossible to 
place concealed wire on non-combustible insulating supports 
of glass or porcelain, the wires may be fished on the loop 
system, if incased throughout in approved continuous flexible 
tubing or conduit. 

j. Wires must not be fished for any great distance, and 
only in places where the Inspector can satisfy himself that 
the above rules have been complied with. 

k. Twin wires must never be employed in this class of 
concealed work. 



* 3 88 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

20. Mouldings : 

a. Must never be used in concealed work or in damp places. 

b. Must have at least two coats of waterproof paint or be 
impregnated with a moisture repellant. 

c. Must be made of two pieces, a backing and capping, 
so constructed as to thoroughly incase the wire and maintain 
a distance of one-half inch between conductors of opposite 
polafity and afford suitable protection from abrasion. 

21. Special, Wiring : 

In breweries, packing-houses, stables, dye houses, paper 
and pulp mills, or other buildings specially liable to moisture 
or acid, or other fumes liable to injure the wires or insulation, 
except where used for pendants, conductors — 

a. Must be separated at least six inches. 

b. Must be provided with an approved water-proof 
covering. (See Definitions.) 

c. Must be carefully put up. 

d. Must be supported by glass or porcelain insulators. No 
switches or fusible cut-outs will be allowed where exposed to 
inflammable gases or dust, or to flyings of combustible material. 

e. Must be protected when passing through floors, walls, 
partitions, timbers, etc., by water-proof, non-combustible, 
insulating tubes, such as glass or porcelain. 

22. Interior Conduits* : (See Definitions.) 

a. Must be continuous from one junction box to another, 
or to fixtures, and must be of material that will resist the 



* The object of a tube or conduit is to facilitate the insertion 01 extrac- 
tion of the conductors to protect them from mechanical injury, and, s 
far as possible, from moisture. Tubes or conduits are to be considered 
merely as raceways, and are not to be relied on for insulation between 
wire and wire, or between the wire and the ground. 



NEW CATECHISM OF ELECTRICITY, 389 

WIRING RULES AND REQUIREMENTS. 

fusion of the wire or wires they contain without igniting the 
conduit. 

b. Must not be of such material or construction that the 
insulation of the conductor will ultimately be injured or 
destroyed by the elements of the composition. 

c. Must be first installed as a complete conduit system, 
without conductors, strings or anything for the purpose of 
drawing in the conductors, and the conductors then to be 
pushed or fished in. The conductors must not be placed in 
position until all mechanical work on the building has been, 
as far as possible, completed. 

d. Must not be so placed as to be subject to mechanical 
injury by saws, chisels or nails. 

e. Must not be supplied with a twin conductor, or two 
separate conductors, in a single tube. (See Rule 22.) 

f. Must have all ends closed with good adhesive material, 
either at junction boxes or elsewhere, whether such ends are 
concealed or exposed. Joints must be made air tight and 
moisture proof. 

g. Conduits must extend at least one inch beyond the 
finished surface of walls or ceilings until the mortar or other 
similar material be entirely dry, when the projection may be 
i educed to half an inch. 

-22,. Double Poi^e; Safety Cut-outs : 

a. Must be in plain sight or enclosed in an approved 
box, readily accessible. (See Definitions.) 

b. Must be placed at every point where a change is 
made in the size of the wire (unless the cut-out in the larger 
wire will protect the smaller). 



39° NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

c. Must be supported on bases of non -combustible, 
insulating, moisture-proof material. 

d. Must be supplied with a plug (or other device for en- 
closing the fusible strip or wire) made of non-combustible 
and moisture-proof material, and so constructed that an arc 
cannot be maintained across its terminals by the fusing of the 
metal. 

e. Must be so placed that on any combination fixture no 
group of lamps requiring a current of six amperes or more 
shall be ultimately dependent upon one cut-out. Special 
permission may be given in writing by the Inspector for 
departure from this rule in case of large chandeliers. 

/. All cut-out blocks must be stamped with their 
maximum safe-carrying capacity in amperes. 

24. Safety Fuses : 

a. Must all be stamped or otherwise marked with the 
number of amperes they will carry indefinitely without 
melting. 

b. Must have fusible wires or strips (where the plug or 
equivalent device is uot used), with contact surfaces or tips 
of harder metal, soldered or otherwise, having perfect electri- 
cal connections with the fusible part of the strip. 

c. Must all be so proportioned to the conductors they 
are intended to protect that they will melt before the 
maximum safe-carrying capacity of the wire is exceeded. 

25. Table; of Capacity of Wires : 

It must be clearly understood that the size of the fuse 
depends upon the size of the smallest conductor it protects, 



NEW CATECHISM OF ELECTRICITY. 



391 



Wig. 172. 




BROWN & SHARPK WIRE) GUAGB (B. & S. W, G.) 



392 NEW CATECHISM OF ELECTRICITY, 

WIRING RULES AND REQUIREMENTS. 

and not upon the amount of current to be used on the circuit. 
Below is a table showing the safe-carrying capacity of conduct- 
ors of different sizes in Brown & Sharpe gauge, which must 
be followed in the placing of interior conductors : 

Table A. Table B. 

Concealed Work. Open Work. 

B. & S. G. Amperes. Amperes, 

oooo 218 312 

coo 181 262 

00 *. 150 220 

o 125 185 

1 105 156 

2 88 131 

3 75 no 

4 :• 63 92 

5 53 77 

6 45 65 

8 33 46 

10 25 32 

12 17 23 

14 12 16 

16 6 8 

18 3 5 

Note. — By "open work" is meant construction which 
admits of all parts of the surface of the insulating covering of 
the wire being surrounded by free air. The carrying capacity 
of 16 and 18 wire is given, but no wire smaller than 14 is to 
be used except as allowed under Rules 18 (a) and 27 (d). 

26. Switches : 

a. Must be mounted on moisture-proof and non -com- 
bustible bases, such as slate or porcelain. 

b. Must be double pole when the circuits which they 
control supply more than six 16 candle-power lamps, or their 
equivalent, 



NEW CATECHISM OF ELECTRICITY. 393 

NATIONAL BOARD FIRE UNDERWRITERS. 

c. Must have a firm and secure contact ; must make and 
break readily, and not stop when motion has once been 
imparted by the handle. 

d. Must have carrying capacity sufficient to prevent 
heating. 

e. Must be placed in dry, accessible places, and be 
grouped as far as possible, being mounted — when practicable 
— upon slate or equally non-combustible back boards. 
Jackknife switches, whether provided with friction or spring 
stops, must be so placed that gravity will tend to open rather 
than close the switch. 

27. Fixture work. 

a. In all cases where conductors are concealed within 
or attached to gas fixtures, the latter must be insulated from 
the gas pipe system of the building by means of approved 
joints. The insulating material used in such joints must be 
of a substance not affected by gas, and that will not shrink or 
crack by varation in temperature. Insulating joints, with soft 
rubber in their construction, will not be approved. (See 
Definitions. ) 

b. Supply conductors and especially the splices to 
fixture wires, must be kept clear of the grounded part of gas 
pipes, and where shells are used the latter must be constructed 
in a manner affording sufficient area to allow this requirement. 

c. When fixtures are wired outside, the conductors must 
be so secured as not to be cut or abraded by the pressure of 
the fastenings or motion of the fixture. 

d. All conductors for fixture work must have a water- 
proof insulation that is durable and not easily abraded, and 



394 NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

must not in any case be smaller than No. 18 B. & S., No. 20 
B. W. G., No. 2 B. S. G. 

e. All burrs or fins must be removed before the con- 
ductors are drawn into a fixture. 

f. The tendency to condensation within the pipes should 
be guarded against by sealing the upper end of the fixture 

g. No combination fixture in which the conductors are 
concealed in a space less than one-fourth inch between the 
inside pipe and the outside casing will be approved. 

h. Kach fixture must be tested for "contacts" between 
conductors and fixtures, for " short circuits," and for ground 
connections before the fixture is connected to its supply 
conductors. 

i. Ceiling blocks of fixtures shonld be made of insulating 
material ; if not, the wires in passing through the plate must 
be surrounded with hard rubber tubing. 

28. Arc Lights on Low Potential Circuits : 

a. Must be supplied by branch conductors not smaller 
than No. 12 B. & S. gauge. 

b. Must be connected with main conductors only through 
double pole cut-outs. 

c. Must only be furnished with such resistances or regu- 
lators as are enclosed in non-combustible material, such 
resistances being treated as stoves. 

Incandescent lamps must not be used for resistance 

devices. . 

d. Must be supplied with globes and protected as in the 
case of arc lights on high potential circuits. 






NEW CATECHISM OF ELECTRICITY. 395 

NATIONAL BOARD FIRE UNDERWRITERS. 

29. Ki<ECtric Gas Lighting : 

Where electric gas lighting is to be used on the same 
fixture with the electric light — 

a. No part of the gas piping or fixture shall be in 
electrical connection with the gas lighting circuit. 

b. The wires used with the fixtures must have a non- 
inflammable insulation, or, where concealed between the pipe 
and the shell of the fixture, the insulation must be such as 
required for fixture wiring for the electric light. 

c. The whole installation must test free from " grounds. * ' 

d. The two installations must test perfectly free from 
connection with each other. 

30. Sockets : 

a. No portion of the lamp socket exposed to contact 
with outside objects must be allowed to come into electrical 
contact with either of the conductors. 

b. In rooms where inflammable gases may exist, or where 
the atmosphere is damp, the incandescent lamp and socket 
should be enclosed in a vapor-tight globe. 

31. Fi3xibi,e Cord : 

a. Must be made of conductors, each surrounded with a 
moisture-proof and non-inflammable layer, and further 
insulated from each other by a mechanical separator of 
carbonized material. Bach of these conductors must be 
composed of several strands. 

b. Must not sustain more than one light not exceeding 
50 candle-power. 



39^ NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

c. Must not be used except for pendants, wiring of 
fixtures and portable lamps or motors. 

d. Must not be used in show windows. 

e. Must be protected by insulating bushings where the 
cord enters the socket. The ends of the cord must be taped 
to prevent fraying of the covering. 

f. Must be so suspended that the entire weight of the 
socket and lamp will be borne by knots under the bushing in 
the socket, and above the point where the cord comes through 
the ceiling block or rosette, in order that the strain may be 
taken from the joints and binding screws. 

g. Must be equipped with keyless sockets as far as prac- 
ticable, and be controlled by wall switches. 

32. Decorative Series Lamps : 

Incandescent lamps run in series circuits shall not be used 
for decorative purposes inside of buildings. 

Class D. Alternating Systems. — Converters or Trans- 
formers. 

33. Converters : 

a. Must not be placed inside of any building, except the 
Central Station, unless by special permission of the Under- 
writers having jurisdiction. 

b. Must not be placed in any but metallic or other non- 
combustible cases. 

c. Must not be attached to the outside walls of build- 
ings, unless separated therefrom by substantial insulating 
supports. 



NEW CATECHISM OF ELECTRICITY. 



3Q7 



Fig. 173. 




UNE CUTOUT. 



Fig. 174. 



Fig. 1T5. 





PORCEIyAIN INSULATORS. 



Fig. 176. 




WOOD CL^AT. 



39^ NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

34. In those Cases where it may not be Possible to 

Exclude the Converters and Primary Wires 
Entirely from the Building, the Following 
Precautions must be Strictly Observed : 
Converters must be located at a point as near as pos- 
sible to that at which the primary wires enter the building, 
and must be placed in a room or vault constructed of, or lined 
with, fire-resisting material, and used only for the purpose. 
They must be effectually insulated from the ground, and the 
room in which they are placed be practically air-tight, except 
that it shall be thoroughly ventilated to the out-door air, if 
possible through a chimney or flue. 

35. Primary Conductors: 

a. Must each be heavily insulated with a coating of 
moisture-poof material from the point of entrance to the 
transformer, and, in addition, must be so covered and pro- 
tected that mechanical injury to them, or contact with them, 
shall be practically impossible. 

b. Must each be furnished, if within a building, with a 
switch and a fusible cut-out where the wires enter the build- 
ing, or where they leave the main line, on the pole or in the 
conduit. These switches should be enclosed in secure and 
fire-proof boxes preferably outside the building. 

c. Must be kept apart at least ten inches, and at the 
same distance from all other conducting bodies when inside a 
building. 

36. Secondary Conductors : 

Must be installed according to the rules for " L,ow Poten 
tial Systems.* ' 



Kew catechism of electricity. 399 

WIRING RULES AND REQUIREMENTS. 

Class E. Electric Railways. 

37. An rules pertaining to arc light wires and stations shall 
apply (so far as possible) to street railway power stations and 
their conductors in connection with' them. 

38. Power Stations : 

Must be equipped in each circuit as it leaves the station 
with an approved automatic " breaker," or other device that 
will immediately cut off the current in case the trolley wires 
become grounded. This device must be mounted on a fire- 
proof base, and in full view and reach of the attendant. (See 
Definitions.) 

39. Troij^ey Wires : 

a. Must be no smaller than No. o, B. & S. copper or No. 
4, B. & S. silicon bronze, and must readily stand the strain 
put upon them when in use. 

b. Must be well insulated from their supports, and in 
case of the side or double pole construction, the supports 
shall also be insulated from the poles immediately outside of 
the trolley wire. 

c. Must be capable of being disconnected at the power 
house, or of being divided into sections, so that in case of fire 
on the railway route the current may be shut off from the 
particular section and not interfere with the work of the fire- 
men. This rule also applies to feeders. 

d. Must be safely protected against contact with all 
other conductors. 



40O NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

40. Car Wiring: 

Must be always run out of reac?i of the passengers, and 
must be insulated with a water-proof insulation. 

41. LIGHTING AND POWER FROM RAILWAY WIRES '. 

Must not be permitted, under any pretense, in the same 
circuit with trolley wires with a ground return, nor shall the 
same dynamo be used for both purposes, except in street rail- 
way cars, electric car houses, and their power station. 

42. Car Houses : 

Must have special cut-outs located at a proper distance out- 
side, so that all circuits within any car house can be cut out 
at one point. 

43. Ground Return Wires : 

Where ground return is used it must be so arranged that 
no difference of potential will exist greater than five volts to 
fifty feet, or fifty volts to the mile between any two points in 
the earth or pipes therein. 

Class P. 

44. Storage or Primary Batteries : 

a. When current for light and power is taken from 
primary or secondary batteries, the same general regulations 
must be observed as applied to similar apparatus fed from 
dynamo generators developing the same difference of 
potential. 



NEW CATECHISM OF ELECTRICITY. 4 01 

WIRING RULES AND REQUIREMENTS. 

. All secondary batteries must be mounted on approved 
insulators. 

c. Special attention is directed to the rules for rooms 
where acid fumes exit. 

d. The use of any metal liable to corrosion must be 
avoided in connections of secondary batteries. 



niscellaneous. 



45. a. The wiring in any building must test free from 
grounds ; i. e. y each main supply line and every branch 
circuit shall have an insulation resistance of at least 25,000 
ohms, and should have an insulation resistance between 
conductors and between all conductors and the ground (not 
including attachments, sockets, receptacles, etc.) of not less 
than the following : 

Up to 10 amperes, . . . . . . 4,000,000 



25 
50 
100 
200 
400 
800 
1,600 



1,000,000 
800,000 
300,000 
160,000 
80,000 
22,000 
11,000 



All cut-outs and safety devices in place in the above. 

Where lamp sockets, receptacles, and electroliers, etc., 
are connected, one-half of the above will be required. 

b. Ground wires for lightning arresters of all classes, and 
ground detectors, must not be attached to gas pipes within the 
building. 



402 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

c. Where telephone, telegraph or other wires connected 
with outside circuits are bunched together within any build- 
ing, or where inside wires are laid in conduit or duct with 
electric light or power wires, the covering of such wires must 
be fire-resisting, or else the wires must be inclosed in an air- 
tight tube or duct. 

d. All conductors connecting with telephone, district 
messenger, burglar- alarm, watch-clock, electric-time, and 
other similar instruments, must be provided near the point of 
entrance to the building with some protective device which 
will operate to shunt the instruments in case of a dangerous 
rise of potential, and will open the circuit and arrest an 
abnormal current flow. Any conductor normally forming an 
innocuous circuit may become a source of fire hazard if crossed 
with another conductor, through which it may become 
charged with a relatively high pressure. (See Definitions.) 

e. The following formula for soldering fluid is suggested : 

Saturated solution of zinc 5 parts 

Alcohol . 4 parts 

Glycerine 1 part 

DEFINITIONS 

of the word APPROVED as used in these rules, and 
notice of the approval of certain wires and mater- 
ials, and the interpretation of certain rules. 

RUI.K 2. Care and Attendance : 

Approved waste cans shall be made of metal, with legs 
raising can three inches from the floor, and with self-closing 
covers. 



NEW CATECHISM OF ELECTRICITY, 



403 




PORCELAIN CLEAT. 
Fig. 178, 




PORCLAIN ROSETTE. 



Fig, 179. 



00 



00OOO 



RUBBER TUBING. 



404 NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

Rule 4. Switchboards : 

Section a. Special attention is called to the fact that 
switchboards should not be built down to the floor, nor up to 
the ceiling, but a space of at least eighteen inches, or two 
feet, should be left between the floor and the board, and 
between the ceiling and the board, in order to prevent fire 
from communicating from the switchboard to the floor or 
ceiling, and also to prevent the forming of a partially con- 
cealed space very liable to be used for storage of rubbish and 
oily waste. 

Rule 5. Resistance Boxes : 

Section a. The word " frame " in this section relates to 
the entire case and surroundings of the rheostat, and not 
alone to the upholding supports. 

Rule 8. Motors : 

Section e. From the nature of the question, the decision 
as to what is an approved case must be left to the Inspector to 
determine in each instance. 

Rule 9. Resistance Boxes : 

Section a. The word " frame'' in this section relates to 
the entire case and surroundings of the rheostat, and not alone 
to the upholding supports. 

Rule 10. Outside Conductors: 

Section a. Iusulation that will be approved for service 
wires must be solid, at least / ¥ of an inch in thickness, and 
covered with a substantial braid. It must not readily carry 



NEW CATECHISM OF ELECTRICITY. 405 

NATIONAL BOARD FIRE UNDERWRITERS. 

fire, must show an insulating resistance of one megohm per 
mile after two weeks* submersion in water at 70 degrees 
Fahrenheit, and three days' submersion in lime water, with a 
current of 550 volts, and after three minutes' electrification. 

Section f. All joints must be soldered, even if made with 
the Mclntyre or any other patent splicing device. This ruling 
applies to joints and splices in all classes of wiring covered by 
these Rules. 

Rule; 12. Interior Conductors: 

Section d. Insulation that will be approved for interior 
conductors must be solid, at least ^\ of an inch in thickness, 
and covered with a substantial braid. It must not readily 
carry fire, must show an insulating resistance of one megohm 
per mile after two weeks' submersion in water at 70 degrees 
Fahrenheit, and three days' submersion in lime water, with a 
current of 550 volts, and after three minutes' electrification. 

Rule 13. Arc Lamps : 

Section c. The hand switch is to be approved, if placed 
any where except on the lamp itself, must comply with 
requirements for switches on hanger-boards as laid down in 
Section g of Rule 13. 

Section f. An approved spark arrester is one which 
will so close the upper orifice of the globe that it will 
be impossible for any sparks thrown off by the carbons to 
escape. 

Rule 15. Outside Overhead Conductors : 

Section b. An approved fusible cut-out must comply with 
the sections of Rules 23 and 24 describing fuses and cut-outs. 



40S NEW CATECHISM OF ELECTRICITY. 



WIRING RULES AND REQUIREMENTS. 

The cut-out required by this section must be placed so as to 
protect the switch required by Rule 17. 

Rule 16. Underground* Conductors : 

Section b. The cut-out required by this section must be 
placed so as to protect the switch. 

Rule 17 : 

The switch required by this rule to be approved must be 
double pole, must plainly indicate whether the current is 
" on " or " off," and must comply with Sections a, c y d and e 
of Rule 26 relating to switches. 

Rule 18. Conductors : 

Section a. In so-called " concealed " wiring, moulding 
and conduit work, and in places liable to be exposed to damp- 
ness, the insulating covering of the wire, to be approved, must 
be solid, at least ^\ of an inch in thickness, and covered with 
a substantial braid. It must not readily carry fire, must show 
an insulating resistance of one megohm per mile after two 
weeks' submersion in water at 70 degrees Fahrenheit, and 
three days' submersion in lime water, with a current of 550 
volts, and after three minutes' electrification. 

For work which is entirely exposed to view throughout 
the whole interior circuits, and not liable to be exposed to 
dampness, a wire with an insulating covering that will not 
support combustion, will resist abrasion, is at least T \ of an 
inch in thickness, and thoroughly impregnated with a 
moisture repellant, will be approved. 



NEW CATECHISM OF ELECTRICITY. 407 



NATIONAL BOARD FIRE UNDERWRITERS 

Section b. Second paragraph. Except for floors, and 
for places liable to be exposed to dampness, glass, porcelain, 
ntetal sheathed Interior Conduit and Vulca Tube, when made 
especially for bushings, will be approved. [The two last 
named will not be approved if cut from the usual lengths of 
tube made for conduit work, nor when made without a head 
or flange on one end.] 

Section/. All joints must be soldered, even if made with 
the Mclntyre or any other patent splicing device. This 
ruling applies to joints and splices in all classes of wiring 
covered by these Rules. 

Rule; 21. Special Wiring : 

Section b. The insulating covering of the wire to be 
approved under this section must be solid, at least q\ of an 
inch in thickness and covered with a substantial braid. It 
must not readily carry fire, must show an insulating resistance 
of one megohm per mile after two weeks' submersion in water 
at 70 degrees Farenheit, and three days' submersion in lime 
water, with a current of 550 volts after three minutes' electri- 
fication, and must also withstand a satisfactory test against 
such chemical compounds or mixtures as it will be liable to 
be subjected to in the risk under consideration. 

Rule 22. Interior Conduits : 

The American Circular Loom Co. Tube, the brass-sheathed 
and the iron-armored tubes made by the Interior Conduit and 
Insulation Company, and the Vulca Tube are approved for the 



408 NEW CATECHISM OF ELECTRICITY. 

WIRING RULES AND REQUIREMENTS. 

Note. — The use of two standard wires, either separate or 
twin conductor, in a straight conduit installation is approved 
in the iron -a rmored conduit of the Interior Conduit and Insula- 
tion Company, but not in any of the other approved conduits. 
Rule 22. e.) {See Addenda).) 

Rule 23. Double Pole Safety Cut-outs : 

Section a. To be approved, boxes must be constructed, 
and cut-outs arranged, whether in a box or not, so as to 
obviate any danger of the melted fuse metal coming in con- 
tact with any substance which might be ignited thereby. 

Rule 27. Fixture Work : 

Section a. Insulating joints to be approved must be entire- 
ly made of material that will resist the action of illuminating 
gases, and will not give way or soften under the heat of an 
ordinary gas flame. They shall be so arranged that a deposit 
of moisture will not destroy the insulating effect, and shall 
have an insulating resistance of 250,000 ohms between the gas 
pipe attachments, and be sufficiently strong to resist the 
strain they will be liable to in attachment. 

Rule 38. Power Stations : 

Section a. Automatic circuit breakers should be submitted 
for approval before being used. 

Rule 44. Storage or Primary Batteries : 

Section b. Insulators for mounting secondary batteries 
to be approved must be non-combustible, such as glass, or 
thorougly vitrified and glazed porcelain. 



NEW CATECHISM OF ELECTPICITY. 



409 



Fig. 180. 



I 



I 



INSIDE WIRING. 



Fig. 181. 




CLEAT COVER. 



<\ 



\ 



Fig. 183. 



n 



Fig. 182. 




CI,EAT. 



Fig. 184. 



COVERED 
WIRE. 



Fig. 185. 




Fig. 186. 




DOUBLE-POINTED TACK& 



410 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

Rui,K 45. Wire: Protectors : 

Protectors must have a non-combustible, insulating base, 
and the cover to be provided with a lock similar to the lock 
now placed on telephone apparatus or some equally secure 
fastening, and to be installed under the following require- 
ments : 

1. The protector to be located at the point where the 
wires enter the building, either immediately inside or outside 
of the same. If outside, the protector to be inclosed in a 
metallic waterproof case. 

2. If the protector is placed inside of building, the wires 
of the circuit from the support outside to the binding posts of 
the protector to be of such insulation as is approved for ser- 
vice wires of electric light and power, and the holes through 
the outer wall to be protected by bushing the same as required 
for electric light and power service wires. 

3. The wires from the point of entrance to the protector 
to be run in accordance with rules for high potential wires ; 
i. e. y free of contact with building, and supported on non-com- 
bustible insulators. 

4. The ground wire shall be insulated, not smaller than 
No. 16 B. & S. gauge. This ground wire shall be kept at 
least three (3) inches from all conductors,, and shall never be 
secured by uninsulated, double-pointed tacks. 

5. The ground wire shall be attached to a water pipe, if 
possible ; otherwise may be attached to a gas pipe. The 
ground wire shall be carried to and attached to the pipe 
outside of the first joint or coupling inside the foundation 
walls, and the connection shall be made by soldering, if 



NEW CATECHISM OF ELF.CTRTCITY. 411 

WIRING RULES AND REQUIREMENTS. 

possible. In the absence of other good ground, the ground 
shall be made by means of a metallic plate or a bunch of wires 
buried in a permanently moist earth. 



Addenda. 



In addition to the foregoing Rules and Requirements, the 
New York Board of Fire Underwriters will require as follows : 

Underground Conductors : (See Rule 16.) 

Must end outside of the main walls of the building and 
not be brought into a building where it is possible to avoid it ; 
and when brought into the building, or any vault or area 
connected with same, must be removed at least two feet from 
all combustible material and kept free and clear of contact 
with any conducting material. 

Rule; 22. Interior Conduits : 

e. Must not be supplied with a twin conductor, or two 
separate conductors, in a single tube, unless the said two 
separate conductors, or twin conductor having an approved 
insulation, are enclosed in a complete, fully insulated, con- 
tinuous iron conduit, and are in circuits installed as per table 
of Capacity of Wires (see Rule 25) for currents not to exceed 
100 amperes. 

The Rules and Regulations of the Board of Electrical Control and alj 
existing regulations of 1'he Local Authorities in reference to the stringing 
of wires, must be strictly observed. 



4 12 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

Central, Stations— Testing : 

Companies furnishing electricity from Central Stations 
must enter into an agreement with the New York Board of 
Fire Underwriters, binding themselves to test their lines for 
ground connections at least once every day (and preferably 
three times per day), and report the result of such test to the 
Board weekly. 

Electric Lights and Motors in General Storage 
Stores : 
Incandescent electric lights may be permitted when the 
entire plant is in full compliance with the rules of the Board, 
and an approved device, working automatically, is provided 
to cut out of building all the electric current when any 
excessive load is developed from any cause, and a certificate 
is issued to that effect ; provided the warehousemen will agree, 
in writing, to discontinue the use of lanterns and use no other 
lights (except in office ) than the fixed incandescent lights 
that may be approved, and not to permit any alterations to be 
made in the electric plant after the certificate is issued, with- 
out the written consent of this Board ; it being understood 
that in case the electric plant is unable to run by reason of 
breakdown or accident, then lanterns as provided for in rules 
for Storage Stores may be used. 

Electric power will be permitted for hoisting only, when 
the wires and motor are fully protected from contact with 
goods on storage and are placed as may be previously agreed 
upon with this Board, and a certificate issued that all is in full 
compliance with the Rules and Regulations of the Board. 



NEW CATECHISM OF ELECTRICITY. ^3 



WIRING RULES AND REQUIREMENTS. 

Electric Heating and Cooking Apparatus ; also Glue 
Pots, Sad Irons, Curling Irons, Etc. 

Electric heaters, Ranges and Stoves : 

a. These must be placed in safe situations (out of easy 
reach of inflammable materials) and separated from and sup- 
ported on non-conducting and incombustible standards or bases 
so as to be at least four inches from woodwork of any descrip- 
tion or other inflammable material, unless protected by 
non-combustible materials such as sheet metal and asbestos, 
or the like, so combined as to prevent appreciable transmission 
of heat, while securing full insulation. The heating wires or 
resistances of these heaters, etc., must be inclosed in non-com- 
bustible cases adapted to prevent accidental contact with any 
exterior object or material. These electric Heaters, Stoves, 
etc., must never be concealed, but must be at all times in 
plain sight. 

b. They must have double pole switches, cut-outs, etc., 
arranged as required for electric lights or power apparatus 
employing the same current and potential. 

c. The attachment of feed-wires to "heaters," etc., 
must be in plain sight, easily accessible and protected from 
interference, accidental or otherwise. 

d. Attachment of conductors to "heaters," etc., must 
be securely made in the same manner that conductors are 
attached to motors or generators dealing with currents equal 
to those employed in these devices, and such conductors 
must be continuous from the ''heater" etc., to the switch or 



4 X 4 NEW CATECHISM OF ELECTRICITY. 

NATIONAL BOARD FIRE UNDERWRITERS. 

cut-out, which must not be within two feet of said " heaters " 
etc. These conductors must be thoroughly well insulated 
and also covered with a good mechanical protection. 

PORTABLE COOKING APPARATUS, GLJJE POTS, CURBING 
IRONS, ET, 

a. The heating coils or resistances of these instruments 
must be inclosed in non-combustible cases, which in turn 
must be mounted on non-conducting and incombustible bases 
raising the same at least one inch from any surface on which 
they stand. 

b. These instruments must not be attached to lanp 
sockets, and when current of more than ten amperes is 
required they must conform to the same rules as Heaters, 
Ranges, etc. 

c. Where currents of ten amperes or less are required, 
these instruments may be connected by specifically approved 
flexible double or twin-wire conductors, provided such con- 
ductor is composed of two multi-strand conductors, each of 
which is insulated by a waterproof material and asbestos 
while; both are surrounded by a covering affording adequate 
mechanical protection. These flexible cords must also be 
connected to "plug switches " having double-pole fuses in 
their sockets which will cut out the circuits if a cross connec- 
tion should occur in the flexible conductor. Moreover, 
such "plug switch " must be so arranged that the plug wil* 
pull out and break the connection if an abnormal mechanical 
strain is brought on the flexible conductor. 



KEW CATECHISM OF ELECTRICITY. 415 

EDISON CONDUIT JUNCTION BOX. 
Fig. 187. 




COVER. 



Fig. 188. 




OPEN. 



Fig. 189. 




CltOSED, 



416 



NEW CATECHISM OF ELECTRICITY. 



WIRING RULES AND REQUIREMENTS. 

The leading-in wires of these flexible cords must be con- 
nected to heaters or the like at the point of lowest temperature, 
and where such wires are detachable at the heater, their 
terminals must be arranged with female ends protected by 
porcelain extending at least one- eighth inch beyond the metal 
terminals. 

If the connection at the heater is fixed, a separable double- 
pole connector must be placed in the circuit so that in case an 
undue strain is brought on the conductors the device will be 
automatically cut out and disconnected. 

Flexible cord connections longer than six feet will not be 
permitted. 

Receptacles for plug attachments must be placed at least 
six inches above the floor. 

Where switches are provided they must conform to the 
rules laid down in Section 26 of the General Requirements. 

Where a number of utensils are grouped for general 
cooking service, installations to be approved must be provided 
with slate, soapstone or other approved slab or table for 
utensils to rest upon. Plug receptacles mounted on slate or 
other approved material shall be attached to mains running 
at least six inches above the working surface of the table. 

Sad irons and other heating appliances that are intended 
to be applied to inflammable articles, such as clothing, must 
be arranged as above as far as connections, etc., are concealed 
and must also be provided with approved attachments which 
will cut off current when they are not in actual use. 






NEW CATECHISM OF ELECTRICITY. 417 

NATIONAL BOARD FIRE UNDERWRITERS. 

The leading-in wires to these forms of apparatus must be 
connected through porcelain connecting blocks, and the cable 
or cord of the same must be passed through an insulated 
elastic spiral or spring so arranged as to protect the same 
from kinking, chafing or like injury at or near the point of 
connection. 

These conductors must be so placed that they will at all 
times be at least four feet from the floor and well protected 
against contact with water pipes or other possible ground 
connections. 

The use of no flexible cord will be permitted, unless 
specifically approved by this Board. 



4i8 



NEW CATECHISM OF ELECTRICITY. 



Fig. 190. 




CotstnecTors. 
Fig. 191. 




CONNECTORS FOR UNE WORK. 
Fig. 192. 



SLEEVE. 
Fig. 193. 




WESTERN UNION WIRE JOINT. 
Fig. 194. 




MCINTIRE SLEEVE AND JOINT. 



NEW CATECHISM OF 4 ELECTRICITY. 4fg 

WIRING. 

Wire Gauges. — In practice sizes of wires or conductors are 
designated in two ways : first, by measurements in i,oooth of 
an inch, and, secondly, by the number of circular mils they 
contain, a circular mil being a circle one one-thousands of att 
inch in diameter, and the number of these circles contained in 
a cross section of a piece of wire is called a size of so many 
circular mils of cross section, or so many circular mils wire, 
the other being mils diameter. A copper bar one square inch 
in size, contains 1,273,200 circular mils, and a round wire, one 
inch in diameter contains exactly one million circular mils. 

Wire gauges are employed for accurately measuring the 
diameter of a wire, this is done so as to calculate the resistance 
of a given length of such wire. 

Fig. 172, page 391, shows a form of wire guage called the 
round, wire gauge. Notches are cut in the edges. Numbers 
indicating the different sizes of the wire are affixed to each of 
the openings ; the number 5 in the gauge indicates that wire 
that will just pass through straight sides of the opening is No. 
5 wire Brown & Sharp gauge (B. & S, G.) 

Fig. 171, page 385, shows the Birmingham wire gauge (B. 
W. G.) In general electric practice the Brown & Sharp 
(American) Wire Gauge is used for copper wire and the 
Birmingham Wire Gauge for iron wire. 

The Micrometer Wire Gauge is shown in Fig. 170, page 
379. This is a device used for measuring the diameter of a 
wire in the thousandths of an inch. Micro as a prefix denotes 
the millionth part. 



420 



NEW CATECHISM OF ELECTRICITY, 



Fig. 195. 




MODEL TROIylyEY CAR. 



Fig. 196. 





ORNAMENT AT, POT^, CONNECTIONS AND FOUNDATIONS. 



422 NEW CATECHISM OF ELECTRICITY. 



THE ELECTRIC RAILWAY. 



Persons to whom the care of machinery is intrusted should 
know something about that machinery, how to operate it to 
get the best results, how to repair it if it gets out of order, and 
especially how to run it so that repairs will seldom be needed. 

Klectrical machinery is new to many workmen. Its opera- 
tion is somewhat of a mystery. Those who have the care and 
management of such machinery should know enough of the 
construction and operation to handle them intelligently, 
whether it is in the shop, central or t>ower station or on the 
electric railway. 

This is notably true in the development of the electric rail- 
way, where new experiences and new problems are coming up 
continually. These problems are being solved in many cases 
by the engineers in the "inner circle" of the large compa- 
nies, and the knowledge is confined to the favored few. 
Many of the same difficulties and problems come also to the 
men directly in charge of the motors ; men who do not under- 
stand much theory, and who are not informed of what is well 
known to the favored few. 

In view of this withholding of necessary knowledge, the 
reader, especially if connected with the electric railway ser- 



NEW CATECHISM OF ELECTRICITY. 423 

THE ELECTRIC RAILWAY. 

vice, is seriously advised to acquire a knowledge of the gen- 
eral principles of electricity, of the dynamo and motor and 
to then apply them to the special line here explained. 

Briefly, the system of electric car propulsion consists in the 
production of the electric current by mechanical means, its 
transmission through conductors to the electric motors on the 
cars, where it is again transformed into mechanical energy, 
which gives the motion to the car. 

The current which drives the motors may be derived from 
two sources : i, from an accumulator carried with the car ; 
2, by a current from a dynamo placed by the side of the con- 
ducting lines, hence outside th^ car. 

The accumulator will be mentioned and described here- 
after. 

The line system may be divided into three divisions ; 
1. The trolley, or overhead system. 
2. The underground system. 
3. The surface system. 



Note. — A, novel plan of making use of both these systems is a combi- 
nation of electric trolley and storage battery in operation upon a suburban 
railway in Hanover, where, after a long trial, it has been adopted. Elec- 
tric accumulators are placed beneath the seats of the cars. The r^ad is 
equipped with trolley wires and motors on one section only. 

While the car is traveling over the trolley section the accumulators are 
charged, receiving a current through the same feed wire as the trolley. 
When the end of the trolley is reached, which is at the city limits, within 
which the overhead wires are prohibited, the car continues on its way 
over a track that was formerly used as a horse car line, relying absolutely 
for power upon the electric energy stored in the accumulators during the 
trip over the trolley road. 



424 NEW CATECHISM OF ELECTRICITY. 

THE ELECTRIC RAILWAY. 

The surface system (3) which is not much used consists in 
an arrangement where the iron or steel tracks are used for 
conductors. 

The underground system (2) is still somewhat in an experi- 
mental stage. It calls for the use of underground * ' conduits ' y 
very similar to those in use in connection with the cable-car 
system of propulsion — but, 

Conduits themselves are exceedingly expensive to con- 
struct, and cannot be operated unless there is a system of sew- 
erage in connection with them, and in case of damage are 
exceedingly difficult to repair. 

Hence the system known as the " Trolley " line has come 
into such general favor that nearly one thousand million 
dollars have already been invested in the system in the United 
States alone. 

The Trolley Wheel is represented in Fig. 239 ; there are 
various forms of it, but usually they are made of brass, about 
five inches in diameter, mounted on the end of a pole about 
12 feet long, bent over as shown in Figs. 195 and 197. The 
end of this pole sets in a frame attached to the car roof, and 
springs acting on the lower end press the wheel against the 
trolley wire. The pole may be of wood or steel. 

The action of the wheel is such that it does not increase 
the sag of the wire but tends to push it up a little in its pass- 
age. 



NEW CATECHISM OF ELECTRICITY. 



425 



Fig. 197. 






r 




^ 



\ —I 




% 



X 




OVERHEAD TRANSMISSION. 



426 NEW CATECHISM OF ELECTRICITY. 

THE ELECTRIC RAILWAY. 

The practical operation of the trolley system is shown in 
full page figure, where the current, as shown by the arrows, is 
taken from the dynamo to the switch board, thence directly 
to the trolley wire or conductor, passing along in the direction 
shown by the arrows, a portion being conducted off at the 
points T T (the remainder going on to supply the other cars), 
where it passes down through the trolley arm, along the wires 
concealed in the car to the motors, through the motors, 
thence to the rails as indicated on the diagram, back to the 
switch board and through the various appliances used there to 
the dynamo, thus making a complete circuit. 

Where long lines are used wires are run out from the sta- 
tion and connected to the overhead trolley wire at suitable 
points, in order that the electrical pressure may be kept prac- 
tically constant. These wires are known as " feeder wires." 

The Motor.-^-The electric motor for street car propulsion 
is simply an appliance for the transmission of electrical into 
mechanical energy, and in action is just opposite to a dynamo 
machine (see Fig. 198). 

One end of the armature shaft of the motor is provided 
with a pinion which communicates its motion by means of a 
large gear to an auxiliary shaft provided with a pinion which 
in turn communicates its motion to another large gear placed 
upon the car axle. In order to insure the parallelism of these 
gears and pinions one end of the motor is fastened directly to 
the car axle, the other end is supported by springs, which 



NEW CATECHISM OF ELECTRICITY. 



427 



THE ELECTRIC RAILWAY. 



Fig. 198. 




STREET: CAR MOTOR. 



428 NEW CATECHISM OF ELECTRICITY. 

THE ELECTRIC RAILWAY. 

permits of a movement of the motor and does away with the 
jar and strain which would otherwise occur on the starting 
and stopping of the car. 

The Railway Motor Controllers now in use are in many 
respects, the most perfect devices ever employed for the pur- 
pose. They are the result of a gradual development from the 
earliest types, and in details of construction, perfection of 
workmanship and certainty of action they are undoubtedly 
enormously superior to all of the original styles. 

There are several methods of governing the speed of the 
electric motor. In some systems a rheostat or resistance is 
connected in series with the armature, this rheostat being 
governed by mechanism placed at each end of the car, known 
as the " controller stand." This controller stand is provided 
with a handle, by means of which the amount of current 
which flows through the motor and the speed may be easily 
regulated. 

Fig. 199 shows very clearly the interior of the type K2 as 
now made by the General Klectric Co. At the left of the 
center of the figure, extending from the top downward, the 
main controlling contact is shown, consisting of arcs or seg- 
ments of circles, each of which terminates in a removable 
copper contact tip. The twelve contact fingers are shown at 
the left. Above, at the right, are shown the eight fingers and 
contacts of the reversing cylinder. 

Near the bottom of the controller at the left are the two 
cut-out handles, the raising of which cuts out either No. 1 or 



NEW CATECHISM OF ELECTRICITY. 



429 



Fig. 199 c 




RAILWAY MOTOR CONTROLLER. 



430 NEW CATECHISM OF ELECTRICITY. 

THE ELECTRIC RAILWAY. 

No. 2 motor as may be desired, at the same time locking the 
main controlling drum so that it can not be turned to the 
points corresponding to the parallel combination, no matter 
which motor may be cut out of the circuit. Near the bottom 
at the right is the main terminal board with its fifteen main 
terminals and just above is seen the heavy electro-magnet, 
designed for blowing out the arcs formed at the tips of the 
contact fingers. 

The magnet is connected in on the main circuit, and what- 
ever current is being used by the car at any time passes 
through its coil, so that the heavier the current and the con- 
sequent tendency to arc, the stronger is the field magnetism 
of the magnet and its corresponding power for blowing out 
the arc. One pole of the magnet is hinged and swings out- 
ward, exposing the fingers, as it is shown outlined against the 
cover of the controller. When closed this pole is directly over 
the finger tips, the other pole being formed by the heavy iron 
casting composing the back of the controller. • 

Each car is provided with a revervsing switch, by means of 
which the direction of the current may be changed, which 
results in changing the direction of the rotation of the arma- 
ture, thus entirely obviating the necessity of turntables, or 
anything of like nature, and checking the car in a case of 
great emergency to avoid accident or collision. Kach car is 
also provided with lightning arresters embodying the same 
principles as those used in the power station, by means of 
which all danger from lightning discharges is obviated. 



Kew catechism of electricity. 431 

THE ELECTRIC RAILWAY. 

The Electric Locomotive. — The most interesting develop- 
ment of the overhead (trolley) system is, of course, the 96- ton 
electric locomotive. The following data, relating to the 
machine are given by the builders of the electrical part of the 
locomotive, the General Electric Company : Number of 
trucks, 2 ; number of motors, 4 ( 2 to each truck) ; weight on 
driving wheels, 192,000 pounds (96 tons) ; number of driving 
wheels, 8 ; drawbar pull, 42,000 pounds ; starting drawbar 
pull, 60,000 pounds ; gauge, 4 feet 8)4 inches ; diameter of 
drivers, 62 inches outside of tires ; length over all, 35 feet ; 
height to top of cab, 14 feet 3 inches. 

This machine has been in operation since August 4th, 
1895, at Baltimore, hauling the entire northbound freight ser- 
vice of the B. and O. railroad. Every train has been 
handled promptly and the locomotive has been ready at any 
and all hours during the day, causing no delay to traffic. 

Up to the present time no train which would hold together 
has been found heavy enough to cause the electric locomotive 
to slip its wheels under ordinary fair conditions. The capacity 
of the locomotive has been by no means reached. 



Note. — Test was made to learn its capacity for running a loaded train 
on an up grade. For this purpose a train consisting of two steam locomo- 
tives, not working, and 27 loaded freight cars, was brought to a stop while 
going north through the tunnel. Here the grade is 42 feet to the mile, 
and the rails were damp and greasy. The weight of the train alone was 
1 125 tons, or 1221 including the electric locomotive. Every drawbar was 
tight, no slack occurring throughout the the length of the train. In this 
condition current was turned into the motors and movement was immedi- 
ately communicated to the train. At the end of one minute the train was 
moving at a speed often and one-half miles an hour, and at this point the 
speed was increased to the usual rate. 



432 



NEW CATECHISM OF ELECTRICITY. 



LINEMEN'S CONSTRUCTION TOOLS. 



Fig. 200. 




Fig. 201. 



pole 

SUPPORT. 



CONNECTORS. 
Fig, 202. 




CONNECTORS. 



Fig. 203. 

)^S8 1 

ipra 



^giliCi 




01 

POLK 
RATCHET. 



NEW CATECHISM OF ELECTRICITY. 433 



LINE WORK. 



Instructions and Cautions for Linemen. -When cutting 
wire, grip the line with the cutting jaws of the pliers and move 
up and down at right angles with the wire two or three times, 
so that you cut the insulation part of the way round on both 
sides ; then hold your pliers firmly, bend the wire once or 
twice 'up and down with your left hand and the wire will break. 
Never try to break the wire by twisting your pliers, unless you 
first move the line out of the cutting jaws. There is no excuse 
for nicks in the cutting jaws of Stub's pliers, and careful line- 
men rarely have it happen. 

In stripping the endsof wire to make a connection, always 
cut along the wire towards the end, in much the same manner 
as if whittling a stick. Never cut round the wire with the 
edge of the knife or pliers, except when cutting the wire. 

In making joints, be careful never to let the cutting jaws 
or edge of your tools "score" the wire. If you do, don't 
cover it up, but make a new joint. 

After a joint is made with not less than four turns each 
side of the connectors, dip or moisten with acid. If you are 
on the ground, dip the joint in melted solder and hold it there 
a few seconds to thoroughly heat the joint, then take it out. 
If well "tinned," dip it in water to remove any acid which 
may be on the ends of the wire near the insulation. 

NOTE _ For very much of the following pages relating to practical 
electric Railroading we are indebted to Jas. I. Ayer, General Manager, St. 
L,ouis, Mo. 



434 



new catechism of electricity. 



LINEMAN'S CONSTRUCTION TOOLS. 

Fig. 205. 



Fig. 204. 




DIGGING 
SHOVEL. 



! 




SPOON 
SHOVEL;. 

Fig. 20S. 



Fig. 206. 



1 



TAMPING 
BAR. 



Fig. 207 



DIGGINC 
BAR. 




SAFETY wire; CUTTERS. 



NEW CATECHISM OF ELECTRICITY. 435 

LINE WORK. 

If where you cannot dip the joint, but have to use the ladle, 
pour the solder frequently over the joint until it leaves a thin, 
smooth coating on the wire. It is not properly done if the 
solder is in lumps or on in a thick layer. 

If you are obliged to use a " blow pot," hold the joint in 
the flame until the solder will easily melt when held against 
the wire after the flame is removed. When this is accom- 
plished, apply the solder with the flame, and not before. 

Solder is put on the joints to keep them from corroding, 
thereby insuring good contact where the two wires come 
together, and is of no use if not well applied. 

After the joint is well cleaned of acid after being soldered, 
paint it thoroughly with insulating compound, then cover 
with a layer of tape, which you will start on one side of the 
joint, against the insulation of the wire, but not over it. Have 
the first layer cover the joint and bare wire only. When this 
is done, paint it, then start back over the joint and tape until 
you have run over the line insulation about two inches, then 
wrap two more layers, painting each when done. 

In wrapping tape, cover what you have half, or lap one- 
half. After four layers are on, paint the whole thoroughly. 

Whenever you find a break in the insulation on the line 
anywhere, paint it first, then tape and paint it. Don't forget 
this. 

In " tying in, " never draw the tie wire so as to bend a kink 
in the line or cut through the insulation with the tie. A tie 
will properly hold the wire in place without drawing it so tight 
as to do either. 



43& 



NEW CATECHISM OF ELECTRICITY. 



LINEMAN'S CONSTRUCTION TOOLS. 
Fig. 309. 




Fig. 310. 



'CUMBERS. 



" CUMBERS." 



Fig. 211. 




LINEMAN'S PUERS. 



NEW CATECHISM OF ELECTRICITY. 437 



LINE WORK. 

In u g pulley blocks on the line, avoid the use of * ' come- 
alongs ' ' when possible, by taking a series of half-hitches, or 
making a " noose wrap " with a small line on the wire to hook 
the block to. If you do use " come-alongs, ' ' see that you do 
not score, cut or kink the wire, and always paint and tape 
broken insulation. 

Groundmen are especially cautioned to watch the line in 
" paying out ' ' and prevent "kinking." Should a short kink 
get pulled into the line, cut it out rather than take the risk of 
its breaking, though you should straighten it out. 

Never use porcelain knobs where exposed to moisture or 
the weather, and never use them anywhere else if glass can 
possibly be used. 

Porcelain knobs circuit breaks may be used where neces- 
sary, providing not more than two lamps are on the loop. In 
making them, paint and insulate with tape the joints in con- 
necting wire of loop. 

In making house connections where wires enter building, 
be sure to have not less than six inches clearance from cor- 
nices of walls. All wiring running over cornices or other 
building projections must be protected with rubber tubing, 
thoroughly taped and painted at the end. Never let a wire, 
however well protected, come in contact with any outside por- 
tion of the building. 

In placing tubing on wire, carefully paint and tape at the 
upper end, leaving the lower end open, so that moisture could 
escape if it got in. 



NEW CATECHISM OF ELECTRICITY. 



Fig. 212. 



LINEMAN'S TOOLS. 
Fig. 213. 




REEL; AND STAND. 



Fig. 214. 




REEL AND STAND. 



Fig. 215. 




BLOCK AND FALLS WITH " COME-ALONGS. 



McINTlRE SPLICING TOOL (FIG. 212.) 



NEW CATECHISM OF ELECTRICITY. 436, 

LINE WORK. 

Always run wires in straight parallel lines, and make 
square turns where possible. Twelve inches between wires is 
the proper space for arc lighting circuits, where practicable. 

Never fasten a cut-out box against the wall. Always place 
glass or porcelain knobs between the box and the wall. 

Never fail to put in "drip-loops" in line where entering 
building. 

In all electrical work, remember where insulation is 
desired it can never be too good, or when contact is desired, 
you can never make it too good or strong. 

In removing lamps ordered out, always close the loop at 
the line where it was originally cut in, and remove all dead 
wire. Never leave dead or unnecessary wire in circuit. 

Always use iron pins on arms where wires turn a corner or 
leave the line. 

Never screw an insulator on iron pin or bracket very tight, 
nor without first putting inside the glass a strip of paper folded 
twice or three times . This will prevent the glass being broken , 
as iron expands with heat nearly twice as rapidly as glass, and 
unless there is room enough, the difference in temperature 
between winter and summer would burst insulators in summer 
which were placed in winter. 

In connecting line to lamps hung from suspension wire, 
put on safety loops by making a half-connection with a short 
flexible wire on each side of the insulators at the pole and on 
the lamp hood. Solder and tape same as other joints. 
Arrange the length of wires leading to lamp so the lamp will 
not shadow the roadway of either street. 



440 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 
Fig. 216. Fig. 220. 



WMMlMtfiiiiU^^UiUUiiilteHtti 



WOOD PIN. 




GLOBE INSULATOR. 



Fig. 217. 



WOOD BRACKET. 



Fig. 221. 




TREE INSULATOR. 



Fig. 218. 




THREE POINT FROG. 



Fig. 222. 




INSULATOR. 



Fig. 219. 




TROLLEY EROG. 



Fig. 223. 



INSULATED 
PLUG. 



NEW CATECHISM OF ELECTRICITY. 



441 



INSTRUCTIONS AND CAUTIONS. 



Do not handle any electric light apparatus while you are 
standing on the ground. 

Never use both of your hands while handling dynamos, or 
anything pertaining to same, while said dynamos are being 
used. 

Fig. 224. 




UNEMAN'S SAE^Y B£l/T. 



Do not touch a water pipe, iron post, or any stone, brick or 
iron structure while in contact with a lamp, line, dynamo, or 
anything connected with the electric light apparatus at the 
same time, unless you are provided with rubber gloves or 
other insulating material. 

When your business necessitates your going through the 
station, keep as far as possible from the machinery and belt- 
ing, and do not meddle with anything unless you are ordered 
by the man in charge, and then only after receiving careful 
instructions. 



442 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 



Fig. 225. 




TE)RMINAI<S. 

Fig. 227. 




Fig. 226. 




WIR3 INSULATOR. 



Fig. 228. 




GUY CI<AMP. 



mmpvmm 



Fig. 229. 



e**MM**k 



Q 



o— B c 



Fig, 230. 



(£ 



rrn cm 



i sM ^ eiir-Tff i TJ i iv"wiT ii. r« N ^-^.,^j.iaj >-wM 

rrn rrn 



tcp cor 




...A 



~IQ COT 



RAIX, JOINTS, 



NEW CATECHISM OF ELECTRICITY. 443 

LINE WORK. 

No one is permitted to in any manner work on the switch- 
boards except when directed so to do by the man in charge of 
dynamo room, and then only after receiving careful instruc- 
tions. 

Keep away from the lightning arresters and wires leading 
to them. 

I/inemen or others operating on lines, must handle each 
and every wire at all times as if it were charged with the elec- 
tric lighting current and grounded. 

When obliged to pass over, under, or by an electric wire, 
avoid touching it in any manner, and especially with any 
uncovered portion of your person. Damp or wet clothing 
makes chance contact with wire dangerous. 

Tools used by linemen and others who ..have occasion to 
work on lamps or apparatus which may be charged with the 
current, must have handles well covered with rubber or other 
insulating material, and it shall be the duty of every lineman 
to look after his tools and see that they are in good condition 
for use, and especially as to the insulation of the handles. 

If it is at any time necessary to stand on the ground or any 
surface not insulated from the ground while handling electric 
wires or apparatus, heavy gum boots or an insulated stool must 
be used ; and under no circumstances allow yourself to make 
contact between two or more wires at the same time. 

Lamp trimmers and others engaged in taking care of and 
trimming lamps, must see that the switch on the board from 
which the lamp hangs is closed before they proceed to handle 
the lamp. Instructions laid down in these rules must be 
observed in connection with the work of handling the lamps. 



444 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 



Fig. 331. 




TREE INSULATORS. 
Fig. 233. 



Fig. 234. 



Fig. 235. 



Fig. 232. 






Fig. 236. 



FEEDER LINE "EARS." 



NEW CATECHISM OF ELECTRICITY. 445 

LINE WORK. 

In the event of any one in any manner being caught on live 
wires, where it is possible to get to them, pull the one caught 
away by grasping any portion of his clothing or body protected 
by clothing. There would be no possible danger to the one 
rendering help, no matter where you may be standing. If the 
one caught should be on a pole or ladder, he could usually 
release himself by kicking himself loose from the supports, or 
drawing up his knees, thereby causing the body to fall. It is 
understood that employees will wear and use their safety belts 
when working above ground on poles or ladders, especially 
when handling wires. 

In working on lines, all circuits must at all times be 
regarded as alive and grounded. With the hundreds of miles 
of wire throughout the city, some of which are carrying heavy 
current at all times, many using ground return, the line you 
are on may p come alive " at any time — be careful. 

Always avoid temporary work. 

When working on poles, be careful to stand so, if you 
should slip or get a shock, you would fall on your belt rather 
than on the wires. 

Avoid leaning over or crowding through wires when possi- 
ble, and do not put yourself in a position where you would fall 
on wires, should an accident occur. 

Always in making connection on poles, work from below 
rather than above, when possible. 

Examine cross arms and see that they are sound and firmly 
fastened before trusting your weight on them. 



446 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 



Fig. 237. 




GLASS INSULATOR. 



NEW CATECHISM OF ELECTRICITY. 447 



LINE WORK. 

Be careful that all tools are securely fastened in your belt 
when working on pole or ladder, and, in handling wires .and 
lines on poles, have a proper regard for the safety of those 
walking or driving below. 

When working on poles, always use your safety belt, as 
well as other safety devices which you are requested to use. 
It takes but a little time to make yourself safe, and many 
weeks to mend a broken bone. 

Never lay tools down when above the ground. 

See that all wires leading out of transformers and out of 
fuse boxes are well taped and painted where they leave the 
transformers, and all transformers must be placed so far from 
doors, balconies, windows and other openings, and sufficiently 
high above ground and roof, as to prevent accidental contact, 
in other words, out of reach. 

Instructions and Cautions for the Dynamo Room. — All 
station employees are requested to study the circuit maps and 
become familiar with the locations of the different circuits. 

On receipt of telephone or other message to cut out any 
circuit for the protection of life and property, do so promptly. 
On an arc circuit, always run the brushes up before pulling 
plugs on switch-board. On incandescent by cutting in resist- 
ance at switch-board to kill the dynamo, then open the switch. 

When a live circuit opens during a run, the dynamo must 
be cut out at once and left out until the trouble is located and 
O. K'd by lineman or inspector. 

Circuits ordered open must be marked on board with col- 
ored chalk. All other circuits must be marked " 0. K." with 



448 NEW CATECHISM OF ELECTRICITY. 

LINE APPLIANCES. 
Fig. 238. 




" COM3-A-I,ONG. ' 



Fig, 239. 




TRO^^Y WHEJKlf. 



NEW CATECHISM OF ELECTRICITY, 449 

LINE WORK. 

white chalk. This must be done only by those authorized so 
to do, and must be reported to man in charge in dynamo 
room. 

Never "try " a circuit with dynamo that opens during a 
run, until the trouble is located, no matter if it " rings' ' 
closed. 

Never connect dynamo to a circuit on which men are at 
work, without instructions from the men to do so. 

When an arc light or motor circuit is reported " O. K." 
after it has been open, build up current very slowly at dynamo 
by hand, and take about five minutes to put full current on, 
because it frequently happens that linemen will leave their 
work and start out on a circuit looking for trouble, without 
first notifying the station. By starting the circuit in this 
manner, should they be in a position where they might feel 
the current, they would likely have warning before current 
reached a dangerous intensity. 

Never run two machines in series. Doing this will be 
sufficient cause for dismissal. No excuse will be accepted for 
disobedience of this rule. 

Rubber mats and gloves must be used when working the 
switch-board. The same rule applies to work on dynamos 
when running. 

An arc made by electricity can frequently be blown or 
whipped out with a towel, on continuous current circuits, and 
should be extinguished in that manner, if the connections 
which occasion the arc cannot be easily separated. 



45o 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 

Fig. 240. 




CIRCUIT BREAKER. 



Fig. 241. 




CIRCUIT BREAKER. 



Fig. 242. 




RUBBER HOOK INSULATOR. 



NEW CATECHISM OF ELECTRICITY. 451 

LINE WORK. 

In the event of a short circuit on alternating lines or 
switches in station, the current can be safely shut off by cut- 
ting in resistance on exciter at switch-board. 

Water will not extinguish an electric arc or fire when pro- 
duced only by the current. 

Large canvas covers are available, which should be quickly 
spread over the dynamos if water is used to extinguish fire on 
the floor above. 

Fire buckets must be kept filled with both sand and water 
on each floor in machine building above engine room. In 
many cases sand will prove more useful than water in extin- 
guishing a fire. The hose on each floor must be kept connected 
and ready for use. 

In using sand or water, remember that a little well directed 
is better than quantities thrown wildly. Use no more of 
either than is absolutely necessary, as it is easy to do more 
damage with them than would be likely by fire. 

Any faulty lamps, wires, belts or anything else reported to 
this department, must have immediate attention from the man 
in charge.* 

No joints are permitted to be made and left without being 
soldered. 

When placing guard wires on street crossings, always use 
iron pins and glass insulators to attach both ends of guard 
wires to. Never tie on cross arm pole. In stormy weather, 
when they may be of use, they would be dangerous every way. 



Yj"- 



NEW CATECHISM OF ELECTRICITY. 



LINE WORK. 

Location of Trolley Wire, — On straight line work the wire 
should be over the center of the track. 

At curves the wire should be placed on the inside of the 
curve, its distance from the center of the track depending on 
the degree of curvature. 

The Repair Shop. — Near the car house, if not under the 
same roof, should be placed the shop for such repairing as is 
profitable for the company to do themselves. The few tools— 
a lathe, drill press, etc. — may be conveniently run by a sta- 
tionary electric motor. 

In the repair shops, perhaps even more than other parts of 
the plant, order and neatness should be the rule. The arma- 
tures should be kept in racks and not on the floors. The 
winders and their supply of wire should be kept away from 
litter of any kind. The floor should be well swept especially 
of all metal filings. Each kind of supply should have a special 
bin, etc., etc. 



Fig. 253. 




In Fig. 253 is con- 
tained a suggestion. As 
each tool should have a 
place it is well, if conven- 
ient, to have a little ' ' sil- 
houette ' ' drawing made 
just under the place a tool 
should be hanging. When 
the tool is away this is a 
reminder to put it back. 



NEW CATECHISM OF ELECTRICITY. 453 



CARE AND MANAGEMENT OF THE 
STREET CAR MOTOR. 



The motor should have exceptionally good care. This can 
only be given by frequent and careful inspection. The 
dynamo and engine in the power house are carefully watched 
and oiled. They are well located and have every advantage ; 
on the same principle the street car motor needs very much 
more care, due to its unfavorable location. 

Washers, carbon dust, bits of gravel, sand, pieces of carbon 
brushes, and other matter capable of doing serious damage, 
have been found in the motor cases of some of the best types. 
The time for inspection is usually brief, but everything must 
be noted. Spare parts should be at hand and no armature or 
field coil in which a defect is suspected to exist should be 
allowed to go on a trip. 

Loose nuts, hot boxes, burnt commutator bars, and matters 
of a kindred nature, should be carefully sought for. Dust or 
mud should not be allowed to accumulate. The screws of the 
motor support should receive minute inspection. Kvery 
screw on the truck is liable to be jarred loose and the dropping 
of the motor into the street is almost certain to wreck the 
greater part of the equipment, both mechanically and electri- 
cally. 



454 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 

Fig. 243. 




WINDING MACHINE. 



Fig. 244. 




Fig. 245. 




BARN OR BRIDGE HANGER. 



Fig. 246. 





TROLLEY CROSS-OVER. 



NEW CATECHISM OF ELECTRICITY. 455 



CARE OF THE MOTOR. 

The motorman should be present when his motor is taken 
apart and inspected. By this means he will become familiar 
with the various parts and their diseases. The motor is under 
his care the greater part of the time and therefore the more he 
knows of its construction the fewer accidents there will be. 

The car should be provided with a monkey wrench, a few 
duplicates of the most important bolts and nuts, a pair of 
pliers, some rubber tape and a supply of insulated copper 
wire about No. 8 B. & S. With these simple toolaand mater- 
ials vexatious delays can often be avoided. 

Run carefully over curves, crossings and switches and thus 
save both them and the motors. 

With a little practice the motorman can accustom himself 
to the ordinary sights, sounds and smells on and about a car 
equipment and anything unusual will at once be detected. 

The one thing that is most liable to derange the mechanical 
portion of a car equipment is vibration. This is largely met 
by a properly designed truck, but a careful motorman can 
also do much to reduce this evil. 

Feeder Wires. — In electric railways the feeder wire sup- 
plies the current from the generator, to the trolley wires. In 
lighting systems it is the main wire coming from the dynamo. 
Feeder cables are always made of stranded — or more than one 
wire, 



45$ 



NEW CATECHISM OF ELECTRICITY. 



LINE APPLIANCES. 



Fig. 248. 



Fig. 351. 




hanger" and "ear." 



Fig. 249. 




SINGLE "PULL-OFE" AND EAR. 



FIG. 250. 





Fig. 252. 




DOUBLE "PULT,-0FE" AND EAR. 



WIRE TIES. 



NEW CATECHISM OF ELECTRICITY. 



457 



STORAGE BATTERIES. 






These are also known as accumulators from the fact that 
they accumulate or store electric energy ; they are also called 
secondary batteries in distinction to primary 
batteries described on page 47. 

These various terms are applied either to a 
single cell or to a collection 
of cells electrically connected 
together. 

Secondary batteries are 
in no sense generators of 
electricity but are employed 
to accumulate, or store, a 
given quantity of electric 
energy, the quantity of which 
is estimated by the numbers 
of hours required to dis- 
Fig. 254. charge it at a given rate. 

While the electric energy may be produced by a primary 
battery, it is usually stored by the use of a dynamo, as shown 
in Fig. 255. 

During the " charging" process the electric energy is 
accumulated and during the discharge the chemical processes 
are reversed, the electric energy flowing from the battery until 
the materials are restored to their original chemical condition. 









45^ NEW CATECHISM OF ELECTRICITY. 



STORAGE BATTERIES. 

Accumulators are coming into rapid application in many 
different ways. Following is a list of some, in which accumu- 
lators are giving highly satisfactory results : 

Electric locomotives for hauling in factories and mines. 
Carriage propulsion. 

Electric launch propulsion. 
Train lighting. 

Yacht lighting. 

Carriage lighting. 

Bic3'cle lighting. 

Miners' lamps. 
Medical, surgical and laboratory work. 
Phonographs. 

Sewing machine motors. 
Fan motors. 

Electric fire-alarm. 

Heat regulating. 

Railroad signal apparatus. 

For portable use, in connection with phonograph and 
other small motor work and small electric lamps, chloride 
accumulators are put up in sealed rubber jars, enclosed in neat 
hardwood cases, provided with handles and binding posts. 
Various capacities are furnished 'for batteries complete, filled 
with acid, and charged up ready for immediate use. 

But, it is in connection with electric railways and electric 
light and power companies that the greatest advances are 
being made ; in Europe especially, great attention is being 



NEW CATECHISM OF ELECTRICITY. 



459 



STORAGE BATTERIES. 

paid to the subject ; eight years' experience in German cen- 
tral station practice have indicated that the use of storage 
batteries insured a reduction of 33^ per cent, in the engine 
<md boiler capacity and a saving of from 20 to 50 per cent, in 
the coal consumption of a station. 

As a regulator of pressure, in case of fluctuations in the 
load, the value of a storing plant is inestimable. These fluc- 
tuations of load are par- 



Fig. 255. 



STORA G£ 
BATTERY 




^g^ 



ticularly noticeable in 
electric railway plants, 
where the demand is 
constantly rising and 
falling, sometimes 
jumping from almost 
nothing to the maxi- 
mum, and vice versa, in a few seconds. If for no other reason 
than the prevention of severe strain on the engines and gen- 
erators, caused by these fluctuations of demand, a storage- 
plant will soon pay for its installation. 

By the installing of a storage plant many natural but small 
sources of power may be utilized in furnishing light and 
power ; sources which otherwise are not available, because not 
large enough to supply maximum demands. The force of the 
tides, of small water powers from irrigating ditches, and even 
of the wind, come under this heading. 

One plant recently installed consists of a twenty-horse 
power engine, two hundred-light dynamo and a one hundred- 



460 NEW CATECHISM OF ELECTRICITY. 

STORAGE BATTERIES. 

light battery. On special occasions, battery and dynamo 
working together will operate three hundred lights, but under 
ordinary conditions one hundred lights are all that are used. 
By running the engine twice, or at most three times a week, 
for a few hours at a time, the battery is kept properly charged, 
and the owner has ample light of the most satisfactory kind, 
obtainable at all times — day or night. 

The Plantes Cell was the first practical storage battery 
constructed ; it was introduced to the public in 1859. 

Plante's theory of the system of the storage battery is the 
simplest one to understand, which is this : " Under the action 
of the primary current, the (accidulated) water is decom- 
posed ; the oxygen peroxidizes the positive electrode, and the 
hydrogen goes to the negative electrode, which is always more 
or less oxydized by the exposure of the air." 

Undoubtedly many other changes take place, sufficient to 
make the action of a storage battery a mystery, but practically 
we have made no farther advance than the carrying out of 
Plante's theory to more practical and commercial results. 



Note. — In all lead storage batteries, one of the objects desired is to 
obtain a large lead surface for small mass, as the capacity and discharge 
ra.es are strictly proportional to the amount of surface involved. This 
necessary maximum of surface has hitherto been obtained in one of two 
ways. The earlier way was to slowly eat out the lead plates by electro- 
lysis until they had attained the requisite spongy condition, an affair of 
some time and expense. The later way— and the one which is generally 
practiced— is to cast a frame of lead, with raised right-angled ribs on each 
s!de, thus forming little depressed squares, or to punch a lead plate fall of 
holes, which squares or holes are then filled with a pasty mixture of red 
oxide of lead in positive plates, and with litharge in negatives. 



NEW CATECIIISxM OF ELECTPICITY. 



461 



STORAGE BATTERIES. 

The Faure Cell, so-called, marked the second step i 1 
advance; This was introduced in 1881. The improvement 
consisted, in giving the two lead plates a preliminary coating 
of red lead. 

Fig. 256. 







In recent forms of accumulators the red lead or (lithage) 
freshly mixed with dilute sulphuric acid to the form of a paste 
is pressed into the holes of a leaden grid shaped so as to give 
it a good mechanical attachment. 

Fig. 254 represents " the grid " which is not unlike the old 
fashioned " grid-iron." 

The Chloride Accumulator is now being most successfully 
introduced owing greatly to the growing use of storage 
batteries in connection with electric light and power plants. 







H 



. NEW CATECHISM OF ELECTRICITY. 463 

STORAGE BATTERIES. 

Fig. 256 represents the lead lined wood tank in which the 
grids are arranged in svmetrical order as shown in the cut, full 
page, Fig. 257, illustrates the method of arrangement at the sta- 
tion of the Germantown Electric I4ght Co., of Philadelphia. 

This battery consists of one hundred and twenty elements 
of eleven plates each. They are installed on the three-wire 
system, and have a normal discharge rate of one hundred 
amperes on each side, and a capacity at this rate of two 
thousand ampere hours. 

The plates are protected by improved asbestos insulation, 
and are contained in lead- lined wooden tanks set on glass 
insulators, and supported on strong supporting stands, painted 
with acid-proof paint in four rows of two tiers each. 

The special application of a battery in this instance is for 
the purpose of carrying the day load of the station for the 
commercial lighting and power circuit, and also at times to 
carry a portion of the night load. The engines are shut down 
at daylight and the battery carries the whole load until dusk, 
at which time it is thrown out of circuit. It is put into charge 
between midnight and 6 A. M., when the station load is small. 
The cost of charging is practically nothing, as the machinery 
is more efficient and no extra labor is required, while during 
discharge the working force of the station is considerably 
reduced, the battery requiring but slight attention. 



It should always be remembered that we are not pouring something 
into a storage tank to be taken out when desired, as seems to be the 
opinion of some, but that a very sensitive process is being gone through 
that requires care in conducting. 



464 



NEW CATECHISM OF ELECTRICITY. 



Table Showing the Relative Dimensions of Pure Copper 
Wire at 6o° Fahrenheit. 



Number. 
B. W. G. 



Diameter. 
Inch. 



0000 


•454 


000 


.425 


00 


.380 





•34 


I 


.300 


2 


•.284 


3 


.259 


4 


.238 


5 


.22 


6 


.203 


7 


.18 


8 


.165 


9 


. .148 


10 


.134 


11 


.120 


12 


.109 


13 


.095 


14 


.083 


15 


.072 


16 


.065 


17 


.058 


18 


.049 


19 


.042 


20 


.035 


21 


.032 


22 


.028 


23 


.025 


24 


.022 


25 


.020 


26 


.018 


27 


.016 


28 


.014 


29 


.013 


30 


.012 



Area. 

Square 
Inches. 



.1618 
.1419 

•I 134 
.0908 
.0707 

• 633 
.0527 

.0445 
.0380 
.0324 
.0254 
.0214 
.0172 
.0141 
.0113 
.0093 
.0071 
0054 
.0041 
•0033 
.0026 
.0019 
.0014 
.OOIO 
.0008 
.0006 
.0005 
.0004 
.OO03 
.0002 
.0002 
.OOOI 
.OOOI 
.OOOI 



Weight and Length. 



Iybs per 
1000 ft. 



623.92 
546.76 
437- 10 
349-93 
272.43 
244.15 
203.06 

17146 

146.51 

124.74 

98.09 

82.41 

66.30 

54-35 

43-59 

35.96 

27.32 

20.85 

15.69 

12.79 

10.18 

7.27 

5.34 

3.71 

3.10 

2-37 

1.89 

1.46 

1. 21 

.98 

•77 

•59 

•51 

•43 



Iybs. per mile 
1760 yds. 



3294.3 
2886.9 
2307.9 
1847.6 

1438.4 
1289. 1 
1072. 1 

905.3 
773-6 
658.6 
517.8 
435-1 
550.I 
287.0 
230.I 
189.9 
144.2 
I IO. I 
82.8 
67.5 
53-8 
38.4 
28.2 
I9.6 
16.4 

12.5 
10.0 

7.8 
6.4 

5-2 

4.1 
3.1 
2.7 

2.3 



NEW CATECHISM OF ELECTRICITY. 



465 



Table Showing the Relative Dimensions of Pure Copper 
Wire at 6o° Fahrenheit. 



Length and 


Resistance 


Resistance 


and Weight. 


Nearest 
B. &S. 


Ohms per 


Ohms 


Ohms 


Lbs. 


1000 it. 


per mile. 


per lb. 


per Ohm. 




.050 


.26 


.OOO08 


12457.5 


OOOO 


.057 


.30 


.OOOIO 


9566.7 


OOO 


.071 


.38 


.OOOI6 


6114.24 


OO 


.089 


•47 


.00025 


39 l8 -56 


O 


.115 


.60 


.00042 


2375.18 


O-I 


.128 


.67 


.00052 


1907.59 


I 


.154 


.81 


.00076 


1319-50 


2 


.182 


.96 


.OOI06 


940.844 


3-2 


.213 


I.I3 


.00145 


686.911 


3 


.250 


I.32 


.00201 


497.96 


4 


•319 


1.68 


.OO325 


307.822 


5 


•379 


2.00 


.00460 


217.34^ 


6 


.471 


2.49 


.00711 


140.689 


7 


•575 


3-03 


.OI058 


94-543 


8 


.717 


3.78 


.01645 


60.804 


8 


.869 


4-59 


.02416 


4I.39 2 


9-10 


1. 144 


6.04 


.04187 


23.884 


II-IO 


I.498 


7.91 


.07186 


13.916 


12 


I.991 


10.51 


.12679 


7.887 


13 


2-443 


12.90 


.19104 


5.234 


14 


3.069 


16.20 


•30135 


3.318 


15 


4.299 


22.70 


.59137 


1.690 


16 


5.852 


30.90 


I.09596 


.912 


18 


8.427 


44.49 


2.27254 


.440 


19 


IO.081 


53.23 


3 25299 


.307 


20 


13.167 


69.52 


5.54848 


.180 


21 


16.517 


87.21 


8.73038 


.114 


22 


21.329 


112.62 


14-5579 


.069 


23 


25.808 


136.26 


21.3142 


.047 


24 


31.861 


168.23 


32.4863 


.031 


25 


40.3 2 5 


212.91 


52.0367 


.019 


26 


52.669 


278.09 


88.7724 


.Oil 


27 


61.083 


322.52 


1 19. 404 


.008 


28 


71.688 


378.51 


164.462 


.006 


29 



466 



NEW CATECHISM OF ELECTRICITY, 



THE TELEPHONE. 



The telephone is an electrical instrument for the trans- 
mission of speech by the electric current. 

The abbreviation of the familiar name is " TI12 'Phone." 

The thousand or more 
uses the telephone can be 
put to and its manifest 
convenience in rapidly 
transmitting messages 
make it the most remark- 
ably time saver the world 
has ever known. 

In the telephone the 
required improvem e n t s 
have been gradually de- 
veloped, so that at the 
present time, instead of 
communicating telephon- 
ically over even short distances with great difficulty and 
uncertainty, it is now as possible and practicable to carry on 
conversation over a line 200, 500 or 1,000 miles long as to 
converse face to face. 




Fig. 258. 



NEW CATECHISM OF ELECTRICITY. 



467 



THE TELEPHONE. 

Figs. 258 and 259 exhibit the telephone as in practical 
use. 

The main principle of the telephone is electro magnetism, 
as in the telegraph, but with many important differences. 

When compared with telegraphic instruments, the tele- 
phone is found to be exceedingly sensitive. A sounder 
requires about the tenth of an ampere to work- it properly, a 
relay, about the hundredth of an ampere ; but a telephone 
will render speech audible with less than the millionth of an 
ampere, and is, therefore, 
more than ten thousand 
times more sensitive than 
a telegraphic relay. 



In operation a line wire 
terminating in ground 
plates with a telephone in 
circuit at each end is the 
first condition. In the 
combination one instru- 
ment may represent a dy- 
namo and the other a motor. The parts of the telephone 
which need principally to be named and described are : 

1. The Induction Coil. 

2. The Vibrating Diaphragm. 

3. The Transmitter. 

4. The Receiver. 

5. The Carbon Button, etc. 




Fig. 259. 



468 



NEW CATECHISM OF ELECTRICITY. 



The Induction Coil (see Fig. 264), 
consists of a magnet with a coil of insu- 
lated wire surrounding it. In practice, 
the induction coil has a half inch core 
of soft iron wires on which are wound 
three layers of No. 16 wire (A. W. G.), 
and upon this is wound a secondary 
wire, which consists of No. 23 (A. W. 
G.), a sufficient quantity being used to 
make the resistance 
of the secondary 
about 17 ohms. 
The' length of the 
coil between the 
flanges of the spool 
on which it is 
wound is 6 inches. 
Facing the pole of 



Fig. 




MOUTH PIECE. 



Fig. £61. 




TRANSMITTER AND RECEIVER. 



Fig. 262. 




LONG DISTANCE 
TRANSMITTER. 



NEW CATECHISM OF ELECTRICITY. 469 

THE TELEPHONE. 

the magnet is the receiving diaphragm, which consists of a 
thin plate or disc of iron fixed at its edges and set in motion 
by the sound waves which strike it, due to the variations in 
the current passing over the line. 

The Receiver. — See illustrations on page 468. The tele- 
phone applied to the ear is a receiver, while the one which is 
spoken into is the transmitter. 

The Transmitter. — See illustration on page 468. Any 
instrument which produces signals to be transmitted through 
a line or circuit is a transmitter. 

The Diaphragm. — This is a disk of iron thrown into 
motion by the sound waves or by electric impulses. Behind 
this diagram and very close to it is placed a carbon button. 
Between this carbon button and the diaphragm is a small piece 
of platinum which is placed so as to touch both the button and 
diaphragm very lightly. 



Note — The average day's work of the New York telephone system is 
150,000 calls. A peculiarity of the telephone traffic is that, although the 
service is permanent, the great use is crowded into a few hours of the 
day. Ninety per cent, of the calls are made between nine in the morning 
and five in the evening. The high-pressure time is between ten and 
noon, wnen calls pour in at the rate of over 19,000 an hour. 

In the operation of the plant some 1,300 persons are employed. 
About half of these are engaged in handling the traffic, and the rest are 
divided between office construction and inspection departments. 

A telephone operator in the Cortlandt Street exchange can find out in 
a second if one out of over 4,000 subscribers connected to that office is 
" busy," in about five seconds she can know if any one of the 15,000 sub- 
scribers in New York City is "busy " a few seconds more will enable her 
to get the same information regarding any one of 13.000 more subscribers 
in Brooklyn and New Jersey towns, and in a minute or two she can tell 
an inquirer if any particular subscriber in Boston, Buffalo, Philadelphia, 
Pittsburg, Washington, Chicago, or a hundred other places, is or is not 
using his telephone. And all withont leaving her piace— so long an arm 
does the telephone system give to a single young woman. 



470 



NEW CATECHISM OF ELECTRICITY. 



THE TELEPHONE. 

Fig. 263. 




THE BEU, TELEPHONE. 

The Bell Telephone. — In Fig. 263 is shown the construction 
of the Bell telephone in universal use as the receiver. M is a 
bar magnet in a case L, L,. B B is a bobbin or coil of insulated 
wire surrounding one end of the magnet. D is the diaphragm. 
K is the mouth piece. 

The terminals in the coil B B connect with the binding 
screws C C. 

Practical Operation of the Telephone : 

1. Atmospheric sound-waves strike the diaphragm of the 
telephone and cause it to vibrate. 

2. The vibrating diaphragm produces a change in the mag- 
netic field of the telephone. 

3. The changes in the magnetic field induce currents in 
the wire coil of the telephone. 

4. The induced currents are transmitted from the trans- 
mitter telephone through the line to the receiver telephone. 



NEW CATECHISM OF ELECTRICITY. 



471 



Fig. 264. 




INDUCTION COII,. 

Fig. 265. Fig. 266. 




TWO POINT SWITCH. 
Fig. 267. 





SWITCH. 



Fig. 268. 




TWO TWIST INSULATED 
WIRE). 



MAGNE)TO B3LI<. 



472 NEW CATECHISM OF ELECTRICITV. 

THE TELEPHONE. 

5. In the telephone receiver the induction currents pro- 
duce changes of intensity in the magnetic field. 

6. In consequence of these changes in the magnetic field, 
the diaphragm of the receiver is thrown into vibration. 

7. The vibrations of the diaphragm of the telephone 
receiver give rise to air waves, which are propagated to the 
tympanum of the ear. 

Every time the human voice is used vibrations of the air 
are produced and the louder and higher the greater the num- 
ber of vibrations — with each change of tone the diaphragm 
vibrates in sympathy. 

How to Use the Telephone. 

To call Central Office, give the bell crank one sharp turn ; 
then take the hand telephone from the hook, place it firmly 
against the ear and listen for the operator, who should answer, 
" What uumber ? ' ' Give the operator the number of the sub- 
scriber desired, who will then repeat back your order, and 
may, to avoid errors and to expedite the service, ask for 
further information in relation to the station called for. 

In talking, speak directly into the transmitter, with lips 
as close as possible to the mouth-piece. When you are 
through talking return the hand telephone to the hook, give 
the bell crank one sharp turn, to notify the operator that you 
have completed your conversation. 

Speaking clearly and distinctly gives better transmission 
than shouting. It is obvious that the user is part of the 
" system " and by the proper use of his telephone can greatly 
promote the general efficiency of the service. 



NEW CATECHISM OF ELECTRICITY. 



473 



THE TELEPHONE. 
Fig. 269. 




MAGNETO TESTING INSTRUMENT. 



Fig. 270. 




MAGNETO TESTING INSTRUMENT (OPEN.) 



474 NEW CATECHISM OF ELECTRICITY. 

THE TELEPHONE. 

Carbon Telephone. — This is a telephone transmitter based 
on the use of carbon as a material whose resistance is varied 
by the degree of pressure brought to bear upon it. Many car- 
bon telephones have been invented — the Blake transmitter is 
one of the most noted. 

Bi-Telephone . — This is a pair of telephones carried at the 
end of a curved bar or spring so that they fit the head of the 
person using them ; one telephone is held against each ear 
without the use of the hands. 

The Telephone Exchange. — This is the office to which tele- 
phone wires lead in a general telephone system. The value of 
a 'phone to each subscriber depends upon the number of other 
subscribers on the line, or more correctly speaking, on the 
number with whom a subscriber can be placed in direct com- 
munication within any part of city or county or state. 

The Switch Board. — When a person becomes a subscriber to 
a telephone company, the telephone placed in office or resi- 
dence is connected by means of a copper wire to a certain 
point on the switch board in the exchange, and to this same 
switch board all other wires extering this same exchange are 
also connected. Then a cord or loop having terminal plugs 
enables the operator at the switch board to < 'connect in' ' any two 
subscribers. This action on the part of the operator virtually 
creates a private line each and every time a connection is made. 

Note.— The modern telephone exchange is practically the creature of 
accident. For, in 1877, in New Haven, Conn., a number of private tele- 
phone lines were so constructed that they all passed through one office, 
thus minimizing the amount of labor required to test each new circuit 
and keep it in repair. A crude form of switch was used in making the 
tests, anc, on one occasion, an employe all unconsciously so disarranged 
this switch that, in place of the two persons at the 1 espective ends of a pri- 
vate line talking together, two private lines were connected in circuit and 
four points or stations provided with the means of communication. 



NEW CATECHISM OF ELECTRICITY. 475 

THE TELEPHONE. 

The subscriber, in ringing his bell, causes a current of 
electricity to pass through a small coil of wire with an interior 
core, which core, when electrified, attracts a small lever, and 
this lever, in moving, allows the above mentioned drop to fall. 
Consequently, when a person becomes impatient and rings the 
bell of his telephone long and hard, he does not startle the 
telephone office by the noise, as he might be led to suppose ; 
the drop simply falls. 

Under the streets of New York City there is a network of sub- 
ways. The cables contain usually fifty-one pairs of wires, and 
are pulled through the three-inch subway iron pipe called a duct. 

After each wire has been connected with the corresponding 
one in the other cable, hot paraffine is poured over the loose 
wires ; a lead sleeve is slipped over the joint, each end of the 
sleeve being sealed with hot lead, thus making a water and 
air tight connection with the lead covering of each cable. 
Great care must be exercised to prevent the wires of the cable 
from becoming moist or damp, due to poorly connected 
joints, for there would then be electrical leakage, or the resis- 
tance of the wires would be reduced, as water saturated With 
impurities is a good conductor of electricity. 



Notr. The method of drawing a cable through a long stretch of sub- 
way between two manholes is quite ingenious. A man stands in the 
manhole with a bundle of short rods, about three feet in length, with brass 
ends so constructed that one will fit into another and stand a large amount 
of pushing or pulling without parting A rod is inserted in a duct; 
another one is then clamped on and pushed forward, this process of join- 
ing being continued until the first rod appears at the next manhole. The 
last rod has a small rope fastened to it, the latter being in turn joined to 
a No. 6 wire, which is made fast to the end of the cable. A man in ihe 
second manhole disconnects the rods and draws the rope and wire 
through. The latter is made fast to a windlass, and by this means the 
lead cable, weighing about six pounds per foot, is slowly unreeled and 
drawn through the duct. 



470 



NEW CATECHISM OF ELECTRICITY. 



THE TELEGRAPH. 



The telegraph consists in a combination of four things, 
namely : 

A battery, which produces a current of electricity. 

A line wire, which conducts that current from one point 
to another. 

Fig. 271. 




TH£ TRANSMITTING KEY. 



A. transmitting key. 

An electro-magnetic apparatus, which gives out in sounds 
or sounding strokes all the signals which are made by pulsa- 
tions of that current from a distant point. 



NEW CATECHISM OF ELECTRICITY. 477 

THE TELEGRAPH. 

Telegraph companies on their long lines use batteries of 
from twenty to a hundred cells each. 

In telegraphy, it is found necessary to use non-conductors 
wherever the wire is fastened ; for this purpose, glass is prin- 
cipally used for outside wires. The glass "insulator" is 
placed on a wooden pin or " bracket" which is fastened to 
the pole or building on which the wire is to be supported, 
after which the wire is strung and tied to the glass with a 
short piece of iron "tie wire." Inside of offices, hard and 
soft rubber tubes are used where the wires pass through the 
windows, and the copper conducting wires are usually covered 
with a coating of gutta-percha or wrapped with a continuous 
covering of cotton or silk. The latter is principally used as 



Note. — "The public," says the Electrician, in a description of this 
apparatus, " considered the eletric telegraph merely as a pure novelty up 
to the day that it served to bring to justice a man who had committed a 
horrible crime. The telegraph was then recognized as a communicating 
agent of the highest value. 

44 The dispatches exchanged on that occasion are engraved upon brass 
plates that are borne by the very instruments that were used at the time. 
The inscription that the Paddington apparatus bears is as follows : 

" On the first of January, 1S45, the following telegram was received by 
this instrument at the Paddington station : 

" l A murder has just been committed at Salt Hill, and the supposed 
murderer was seen purchasing a first class ticket for I/mdon by the train 
that left Slough at hall past seven o'clock in the evening. He was in the 
garb of a Quaker, with a long brown coat that reached nearly to his feet. 
He is in the last compartment of the second first class coach.' 

M On the first of January, 1845, the following answer was sent from 
Paddington : 

" ' The train has just arrived, and a person answering in all repects to 
the description given by telegraph came out of the compartment named. 
I pointed the individual out to Police Sergeant Williams. The man 
entered a New Road omnibus, and Sergeant Williams got in with him. ,1> 



478 NEW CATECHISM OF ELECTRICITY. 

THE TELEGRAPH. 

a covering for wires inside the finer instruments. For the 
handles or knobs to the various instruments hard rubber is 
generally used. 

The operation of a telegraph is not, as many people sup- 
pose, a complicated or difficult matter to understand. The 
apparatus employed is quite simple, and easily understood. 

The battery is the first essential part of a telegraphic 
apparatus, as it is by the chemical action in the battery that 
the electric current is first generated. In practical telegraphy 
this current is made to traverse long or short distances 
through the conducting medium of metallic wires, and by 
means of the proper instruments, made to give out tangible 
results. 

The basis of the entire telegraphic mechanism is the 
Klectro-magnet and the transmitting "Key," (see Fig. 271.) 
The Klectro-magnet is constructed as follows : two bars of 
soft iron, having round heads of hard rubber, thus making 
spools of each, are joined together by means of a short flat bar 
of iron similarly soft. The round bars in the spool of the 
magnet are called cores, the flat connecting bar at the back is 
called the "back bar/' or "heel piece." The movable flat 
piece of iron in front, which is to be attracted by magnetism 
to the cores, or withdrawn by the spring when no magnetism 
excites the cores, is called the armature, 

A silk or cotton-covered wire is wound in continuous turns 
about the cores, until the diameter of about an inch and a 
half is attained, and each core or spool of the magnet contains 



, 



NEW CATECHISM OF ELECTRICITY. 479 



THE TELEGRAPH. 

a great number of turns of trie wire around it. Now, if a cur- 
rent of electricity be sent through this wire, it will, by its 
passing through the numerous turns, cause the iron cores 
within to become magnetic and to possess the power of 
attracting with considerable force any piece of iron brought 
near to their ends. 

THE MORSE TELEGRAPH ALPHABET. 

h" i ^j_ Bf_ l Ijsl Ja 

OP Q R S T U 

mm ■■••■§ « m um iiii m «• « w • • m t u rn n » • «*■» 

..y_ ..jy_ .J*.. .. Y .. ..?.'.4 6 .. 

Numerals. 

._*_. _.JL §— - .--4 JL_ 

6 7 8 9 

-•»•«»•>« mm mmamm m m mmmmm m mnm m mrnarn m m ■ n i n m 

Punctuation. 
Per iod, Comma, Semi -c olon. Quotation. 

Exclamation* Inte rrogation: Parenthesis. Parag raph. 

The Morse alphabet consists of what are called dots, 
dashes and spaces. Combinations of these make intelligible 
signals. Many of the characters will be found to be the 
reverse of others : such as A is the reverse of N ; B of V ; D 
of U ; C of R ; Q of X ; Z of & ; so if the formation of one of 
these letters be obtained, its reverse is easily mastered. C, 
K, H, I, O, P, R, S, Z, Y, are merely represented by dots and 
spaces, and, if due regard be given to them, they will be found 
very easy to commit to memory, 



480 NEW CATECHISM OF ELECTRICITY. 

THE TELEGRAPH. 

The first step is to memorize the alphabet, so that each 
character can be called to mind at will ; thus, A, dot and dash; 
B, dash and three dots ; C, two dots, space, dot, etc. The 
period is the only punctuation mark in frequent use. 

A dot (K) is made by a single instantaneous, downward 
stroke of the key. A short dash (T) is made by holding the 
key down as long as it takes to make three dots. A long dash 
(Iv or cipher) is made by holding down as long as required to 
make five dots. A cipher is prolonged so as to occupy about 
the time required for seven dots. 

The intervals between dots or dashes in the same letter are 
called breaks. A space in letters should occupy the time 
required for a dot and break. The space between letters 
should occupy the time required for two dots and breaks. 

The space between words should occupy the time required 
for three dots and breaks. 

In letters that do not contain spaces, the dots and dashes 
should follow each other as closely as possible. 

The armature of the magnet is attached to a lever, and this 
lever, which swings on* a pivot in the middle, is provided at 
the end with a pointed pin or screw, which is caused to press 
upwards against a strip of paper whenever the magnet attracts, 
and to return to its former position when the attraction ceases. 
Meanwhile the paper is kept moving steadily forward, so that 
if the lever-pin is pressed against the paper, for only an instant 
of time, a short mark or dot appears pressed or embossed into 



Fig. 272. 




THE MORSE KEY. 
Fig. 273. 




KEY BOARD, 

Fig. 274. 




TElfEORAPH KEY AND RET, AIT. 



482 NEW CATECHISM OF ELECTRICITY. 

THE TELEGRAPH. 

the paper. If for a longer time, the mark would be propor- 
tionately longer, or a dash. If alternately, the marks would 
come consecutively, and have spaces between them. As the 
Morse Alphabet consists entirely of dots, dashes, spaces, and' 
extra long dashes, the letters and numerals are easily made; 
with these marks and their combinations. So that as the: 
hand of the operator, on the key at a distant point, makes, 
short or long strokes, dots or dashes, or spaces, these same 
marks appear on the paper as it comes from the Register, and. 
being based on the formation given by the Morse Alphabet,, 
are as easily understood by the receiving operator as though 
they appeared in the well-known Roman characters. 

It should be remembered that there is no change in the 
tone of a sounder, the letter being determined solely by the 
* ' time or times ' ' the lever is up or down. 

The key is provided with screws for the purpose of regu- 
lating its play to suit the hand of the operator. 

A little practice will enable the learner to judge best for 
himself as to how this should be set. 

The Key is a simple contrivance for making or breaking 
the contacts which control the passage of the current — a steel 
lever, swung on a pivot, having a rubber handle, which the 
operator grasps lightly with the thumb and forefingers. On 
pressing the lever downward, a platina point projecting under 
the lever is brought into contact with another platina point 
set into an insulation of rubber in the base of the key, so that 
there can be no electrical connection between them unless the 



NEW CATECHISM OF ELECTRICITY. 483 

THE TELEGRAPH. 

key is pressed down, or " closed, " as it is termed. A conduct- 
ing wire being separated at any point, and one of its ends 
connected with the lever or base of the key, and the other 
end with the metal set into the rubber insulation, would con- 
vey the current while the key was closed, and cease to do so 
the moment it was opened. Platina is used at the points 
where the electrical contacts are made and broken, because it 
does not readily fuse or tarnish. An extra lever at the side of 
the key is called the " circuit-closer, ' ' and is used as a means 
of keeping the circuit closed when the hand of the operator is 
not on the key. When the circuit-closer is pushed into its 
closed position, it makes contact with a brass Hp, which latter 
is fastened to the rubber along with the lower platina point. 
This, then, has the same effect as though the key was pressed 
downward and contact made at the points. 

Duplex Telegraphy. — There are two distinct methods of 
arranging telegraphic apparatus so as to transmit two messages 
through one wire, one from each end, at the same time. The 
ikst of these, known as the differential method, involves the 
use of instruments wound with differential coils, and is appli- 
cable to special cases. The second method of duplex working, 
known as the Wheatstone's Bridge Method, is capable of much 
more general application. 

The Relay. — In working over long lines, or where there 
are a number of instruments on one circuit, the currents are 
often not strong enough to work the recording instrument 
directly. In such a case there is interposed a relay or repeater. 



484 NEW CATECHISM OF ELECTRICITY. 

THE TELEGRAPH. 

This instrument consists of an electromagnet round which the 
line current flows, and whose delicately poised armature, 
when attracted, makes contact for a local circuit in which a 
local battery and the receiving Morse instrument are included. 
The principle of the relay is, then, that a current too weak to 
do the wo**k itself may set a strong local current to do its work 
for it. 

Another term for this instrument is ' ' the relay magnet. ' ' 

The use of the relay is especially required in the Morse 
system of telegraphy in order to cause the sounder to be more 
distinctly heard ; the use of the relay permits much smaller 
currents to be used than could otherwise be done. 

Faults in Telegraph Lines. — Faults may occur in telegraph 
lines from several causes : either from the breakage of the 
wires or conductors, or from the breakage of the insulators, 
thereby short-circuiting the current through the earth before 
it reaches the distant station, or, as in overhead wires, by two 
conducting wires touching one another. Various modes for 
testing the existence and position of faults are known to tele- 
graph engineers ; they depend upon accurate measurements 
of resistance or of capacity. Thus, if a telegraph cable part in 
mid-ocean it is possible to calculate the distance from the 
shore end to the broken end by comparing the resistance that 
the cable is known to offer per mile with the resistance offered 
by the length up to the fault, and dividing the latter by the 
former. 



NEW CATECHISM OF ELECTRICITY. 485 

THE TELEGRAPH. 

Submarine Telegraphs. — Telegraphic communication be- 
tween two countries separated by a strait or ocean is carried 
on through cables, sunk to the bottom of the sea, which carry 
conducting wires carefully protected by an outer sheath of 
insulating and protecting material. The conductor is usually 
of purest copper wire, weighing from 70 to 400 lbs. per nauti- 
cal mile, made in a sevenfold strand to lessen risk of breaking. 
In the Atlantic cable, which is of the usual type of cable for 
long lines, the core is protected first by a stout layer of gutta- 
percha, then by a woven coating of jute, and outside all an 
external sheath made of ten iron wires, each covered with 
hemp. The shore ends are even more strongly protected by 
external wires. (See Fig. 42, page 97.) 

Culley states that when a current is sent through an 
Atlantic cable from Ireland to Newfoundland no effect is pro- 
duced on the most delicate instrument at the receiving end for 
two-tenths of a second, and that it requires three seconds for 
the current to gain its full strength, rising in an electric wave 
which travels forward through the.cable. The«strength of the 
current falls gradually also when the circuit is broken . 



486 



NEW CATECHISM OF ELECTRICITY. 



ELECTRIC BELLS. 



The electric bell is a bell rung by electricity. 
Generally it is worked by a current exciting an electro- 
magnet attracting or releasing an armature which is attached 




Fig. 275. 
to the vibrating or pivoted tongue of the bell. T*his is done 
alternately so that the tongue beats against the bell. 



NEW CATECHISM OF ELECTRICITY. 487 

ELECTRIC BELLS. 

The arrangements of the instrument are shown in Fig 276, 
in which B is the electro -magnet and H the hammer. A 
battery consisting of one or two Leclanche cells placed at 
some convenient point of the circuit, provides a current when 
required. By touching the i ' push ' ' P, the circuit is com- 
pleted, and a current flows along the line and round the coils 
of the electro-magnet, which forthwith attracts a small piece 
of soft iron attached to the lever, which terminates in the 
hammer H. The lever is itself included in the circuit, the 
current entering it above and quitting it at C by a contact- 
breaker, consisting of a spring tipped with platinum resting 
against the platinum tip of a screw, from which a return wire 
passes back to the zinc pole of the battery. As soon as the 
lever is attracted forward the circuit is broken at C by the 
spring moving away from contact with the screw ; hence the 
current stops, and the electro-magnet ceases to attract the 
armature. The lever and hammer therefore fall back again 
establishing contact at C, whereupon the hammer is once 
more attracted forward, and so on. The push P is shown in 
section on the right of Fig. 277. It usually consists of a 
cylindrical knob of ivory or porcelain capable of moving 
loosely through a hole in a circular support of porcelain or 
wood, and which, when pressed, forces a platinum-tipped 
spring against a metal pin, and so makes electrical contact 
between the two parts of the interrupted circuit. 

The bell may be worked by a distant switch or press button 
ringing once for each movement of the distant switch or it 
may be of the— 



4 8& 



NEW CATECHISM OF ELECTRICITY. 



ELECTRIC BELLS. 

Vibrating Bell Type. — When the current is turned on in 
this system it attracts the armature. As this moves towards 
the poles of the magnet it breaks the circuit by drawing the 
" contact spring " away from the " contact point." 

This opens the circuit as before explained and causes the 
continual ringing. 



Fig. 376. 



Fig. 27t. 




DEFECTS OF ELECTRIC BELL. 

The possible defects of electric bells may be classed under 
four heads, viz.: ist, bad contacts ; 2d, bad adjustment of the 
parts ; 3rd, defective insulation ; 4th, warpage or shrinkage 
of base. Many operators are content with simply turning the 



NEW CATECHISM OF ELECTRICITY. 469 

ELECTRIC BELLS. 

terminal wires round the base of the binding-screws. Unless 
the binding-screws are firmly held down on to the wires by 
means of a back nut, a great loss is sure to occur at these 
points, as the wires may have been put on with sweaty hands, 
when a film of oxide soon forms, which greatly lowers the 
conductivity of the junction. Again, at the junction points 
of the wires with the contact angle brass and contact pillar, 
some workmen solder the junctions, using " killed spirits" 
as a flux. 

If solder be used at any parts, let resin be used as a flux. 
Even if any excess of resin remain on the work, it does no 
harm and does not destroy the insulation of any of the other 
portions. Another point where bad contact may arise is at 
the platinum contacts. Platinum is a metal which does not 
rust easily, even under the influence of the electric spark 
given at the point of contact. Therefore it is preferred to 
every other metal (except, perhaps, iridium) for contact 
breakers. 

As to bad adjustment ; it is evident that the magnets and 
the armature must stand at a certain distance apart to give 
the best effects with a given battery power. The distance 
varies from ^ T ¥ in. in the very smallest, to ^ in. in large bells. 
Sometimes the armature adheres to the poles of the electro- 
magnet ; this is due to residual magnetism^ and points to 
hard or unannealed iron in the cores or armature. As a 
make-shift, this defect may be partially remedied by passing 
a thin piece of paper over that surface of the armature which 
faces the poles of the electro-magnets. 



4^o 



NEW CATECHISM OF ELECTRICITY. 



Fig. 278. 




Fig. 279. 






<F? 






1 


D 


c 



MAGNETO BELT*. 



NEW CATECHISM OF ELECTRICITY. 49I 

ELECTRIC BELLS. 

Another bad adjustment is when the platinum screw does 
not touch fairly on the centre of the platinum speck, but 
touches the spring or the solder. Rust is then sure to form, 
which destroys the goodness of the contact. To adjust the 
contact spring at the right distance from the platinum screw, 
hold the hammer against the bell or gong. The armature 
should now just not touch the poles of the electro-magnet. 
Now screw up the platinum screw until it clears the contact 
spring by about the thickness of a sheet of brown paper 
(say 5V of an inch). I,et the hammer go, and notice whether 
the contact spring makes good contact with the platinum 
screw. When this has been satisfactorily adjusted the back- 
nut or set screw may be tightened to insure that the vibration 
of the hammer shall not alter the adjustment. 

The other points where the insulation may be defective are 
between the binding screws and the base, if this be all of 
metal ; or between the contact spring block and the base, and 
the contact pillar. It is also probable (if the connecting wires 
have not been covered with india rubber tubing, as recom- 
mended) that leakage may be taking place between these 
wires and some portion of the metal work of the base or frame. 
This must be carefully examined. 

Warpage or shrinkage of the base — can only occur in 
badly -made bells, in which the entire base is of wood. A 
cursory examination will show whether the board is warped 
or swollen, or whether it has shrunk. Warping or swelling 
will throw the electro-magnet too far from the armature, or 
''set " the pillar out of place ; shrinkage, on the contrary, will 



/ 



492 NEV ' CATECHISM OF ELECTRICITY. 



r<5> 



CO 




IhQ 



r*^ 






2 




c 



p 



CQ 




-■© 



CQ 





6 

M 



V 



NEW CATECHISM OF ELECTRICITY. 493 

ELECTRIC BELLS. 

bring the parts too close together and jamb the magnets, the 
armature, and the contact pillar into an unworkable position. 

No bell that is set to do real work should be fitted up 
without a cover or case. The dust which is sure to accumu- 
late, not to speak of damp and fumes, etc., will certainly 
militate against good contacts and good action if this important 
point be neglected. 

~ JOINING TWO WIRES. 

Ete. 284. 

J01NING-0N A BRANCH WIRE. 

To make a good joint, the following method of procedure 
should be adopted : — Strip the ends of the wires to be joined 
of their insulation for a length of about i % inches, and scrape 
clean with a knife or brighten with emery paper. Then 
(taking one wire in each hand) twist the wires together as 
shown in Figs. 283 and 284 (Fig. 284 is a branch wire), and 
tighten up with the plier. Now get ready the articles required 
for soldering, which' should consist of the following : — A 
small copper bit, filed wedge shape with an ]/% inch groove 
cut across one face; a small spirit lamp for heating the bit, a 
stick of solder, and lastly, a piece of composite candle or 




494 NEW CATECHISM OF ELECTRICITY. 



ELECTRIC BELLS, 
rosin. The best "blow-pipe" solder should be used, the 
quality of which may be tested by holding it up to the ear and 
bending it, when, if it is good, a peculiar crackling noise will 
be heard, which is known as the ' ' cry of the tin. " To solder 
the joint, heat the bit, previously tinned, in a spirit lamp or 
fire, and wipe with a piece of clean rag, and then, holding it 
with the grooved side upward^ fill the groove with solder. 
Now rub some composite candle or powdered rosin on the 
joint, and lay it in the groove, turning it over till the solder 
runs completely round, when quickly wipe with a piece of 
rag, and the result will be a strong, clean joint. 



CONNECTING UP. 

The following diagrams, 279 to 282, show several ways of 
connecting up bells, indicators, etc., and though the methods 
most usually required are shown, nearly every instance may 
require some little special modification. 

Simple Bell Circuit.- -Pig. 279 shows a simple circuit, con- 
sisting of push, battery, and bell. The cover of the push P 
has been removed, showing the connections to the contact 
springs, ©ne of which, for the purpose of distinction, is 
shown darker than the other. The bell B (shown in detail in 
Fig- 275) has its cover on ; thus none of the movement is 
visible. Z and C are the respective poles of the battery D. 
On the two springs of the push being pressed together the 



NEW CATECHISM 6F ELECTRICITY. 4^5 

ELECTRIC BELLS. 

current flows from the positive pole C of the battery to the 
terminal Iy, through the bell to the terminal K, and thence by 
the wire and push-springs to the negative pole Z. Both in 
this and the following figures the Z or return wire is shown 
thicker, in order to make the diagrams clearer. 

Simple Bell Circuit with "Earth." — Fig. 280 is a simple 
bell circuit with " earth " connections, the circuit being com- 
pleted between the two plates K K by the earth; the wire 
from the zinc of the battery, and one of the wires from the 
push being fastened to the water-pipe or gas-pipe. 

Two or more Pushes to ring same Bell. — Fig. 281 shows 
the method of connecting two or more pushes so as to ring the 
same bell. The pushes are here shown with their covers on, 
the buttons being represented by the black dots. Pressing the 
button of either of the pushes a, b> c> d completes the circuit, 
causing the bell B to ring. 

Two Bells to ring simultaneously from one Push. — Fig. 282 
shows an arrangement by means of which two bells can be 
rung simultaneously from one push, the bells being some dis- 
tance apart, as in separate rooms. On the button of the push 
P being pressed in, the current flows from the positive pole C 
of the battery through the push, and along the wire a to d, 
where it divides, half (if the bells are of equal resistance) pass- 
ing through the bell B, and half through the bell W. When 
bells are arranged parallel like this, care should be taken to 
insure the resistance of the coils of each bell being as near 



49 6 NEW CATECHISM OF ELECTRICITY. 



ELECTRIC BELLS. 

alike as possible, or else to put the bell with the lowest resist- 
ance the furthest from the battery, so that the resistance of 
the line compensates for its lower resistance. If there are 
many bells, care must also be taken to provide sufficient bat- 
tery power, the largest sized cells being used. The practice 
of splitting up a battery of smaller cells into two halves, and 
connecting the halves in parallel, is not advocated, unless 
absolutely necessary, it being far preferable to employ larger 
sized cells. 



Push Buttons.— These are switches (see Figs. 285 and 286) 
for closing a circuit by means of pressure applied to a button. 
The button is applied to a spring so that when pushed in and 
released it springs back ; thus the circuit is closed only as 
long as the button is pressed. 

Pulls.— These are switches for closing a circuit when 
pulled. 

Magneto Bell and Generator.- -Fig. 278 shows a small 
magneto bell and generator, there being also a switch hook 
at the bottom, since the generator is mainly used for tele- 
phony, which is the chief field of the magneto bell. The 
generator is, it will be seen/ fixed in the body of the case, 
while the bell is on the lid. The hammer-head, projecting 
through a hole, works between the two gongs. 

The apparatus required for signalling by the method men- 
tioned above consists of two parts— the generator and the 
bell. The principle on which the generator acts is the same 



NEW CATECHISM OF ELECTRICITY. 497 

ELECTRIC BELLS. 

as that on which is based the action of all dynamos, and, in 
fact, the generator finds in the dynamo almost its exact 
counterparts. 

The Electric Buzzer is a very useful instrument for use 
in places where the ringing of a bell would be an annoyance. 
It operates on the same principle as the electric bell and can 
be adjusted to emit a musical and pleasing hum instead of the 
ordinary ringing. 

The direction of the current cuts no figure in this class of 
work ; connect the opposite ends of the circuit to the opposite 
ends of the circuit to the opposite poles of the battery and the 
circuit is complete. 

Wiring plans and specifications should be worked out by 
electrical engineers rather than architects or builders, as the 
problems of wastage of current and the danger to life and 
property are extremely difficult to work out under all the 
varying conditions. 

" Diagrams " should be made showing in detail the con- 
nections actually required, and these should be provided at 
an early stage of any installation. 



498 



New catechism of electricity, 



ELECTRIC BELLS. 

Explanation of Technical Terms used in Electric=beII 

Work. 

Battery.-The combination of cells which furnish the 
current of electricity for working the bells, indicators, &c. 

C*//._Bach outer jar of the battery, with its two elements 
and exciting fluids constitutes a cell. 



Fig. 285. 



Fig. 386. 




Circuit.— The wires, bells, indicators, batteries, &c, form- 
ing the path for the electricity. 

Defledion.-The angle or number of degrees through 
which the needle of the detector moves during the passage of 
a current round the coils. 

Earth return.-The use of the earth as part of the circuit. 
Earth wire.-The wire from the bell, battery, &c., leading 
to the water or gas pipes. 



NEW CATECHISM OF ELECTRICITY. 499 

ELECTRIC BELLS. 

Fault. — Any break or interruption of the circuit by which 
some of the operations are interfered with. 

Line. — The wire joining one station with another. 

Line Battery. — The battery which is used to send the 
currents to line. 

Local battery. — The battery placed near the bell or appara- 
tus required to be worked which continues the ringing of the 
bell after it has been once started by the current from the 
line battery. 

Local circuit — The circuit through which the current of 
the local battery flows. 

Metallic circuit. — The use of another wire for return 
instead of earth. 

To connect up. — To join the bells, indicators and other 
apparatus included in the circuit. 

To disconnect. — To remove the ends of the wires from the 
terminals of the instrument, thus cutting it out of the circuit. 

To make " earth.'" — To connect the wire to earth. 

A short-circuit. — A fault caused by two wires coming 
together so as to form a shorter path for the current, diverting 
the whole or greater part of it from its proper course. 

To short-circuit a cell. — To join the terminals with a piece 
of wire. 

71? short-circuit an instrument. — To join the terminals of 
the bell, &c, with a piece of wire. 



500 NEW CATECHISM OF ELECTRICITY. 



ELECTRIC PUMPS. 



Pumps suitable for all services are built to be driven by 
electric motors, and special designs have been made to cover 
the requirements of hydraulic elevator service, mine service, 
water works supply, irrigation purposes, fire protection, or in 
short any service where electric motive power can be used to 
advantage. 

The great variety in style and size of these pumps now in 
successful use assures the extension and enlargement of the 
application of electric motors to all k inds of pumping machin- 
ery. 

Fig. 28y~shows a motor attached to a pump with govern- 
ing arrangement which is very simple in construction. The 
pulley of the switch is connected by a chain to a float resting 
upon the water in the tank, so that when the water falls the 
wheel is revolved until the starting point is reached, when it 
causes the switch arm to pass slowly over the contacts until 
the full current is cut in, and the motor runs at full speed. 
As the water rises, through the action of the pump, the pulley 
is turned in the opposite direction, finally making a quick 
break, shutting off the current and stopping the motor. This 
switch is positive in action, and cannot fail to work at all 
times and under all circumstances. It prevents the tank from 
overflowing or becoming empty through neglect of the 
attendant. 



NEW CATECHISM OF ELECTRICITY. 



50I 



ELECTRIC PUMPS. 



Fig. 287. 




EI3CTRIC PUMP AND AUTOMATIC TANK SWITCH. 



502 NEW CATECHISM OF ELECTRICITY. 



ELECTROMETALLURGY. 



The applications of electro-chemistry to the industries are 
three-fold. Firstly, to the reduction of metals from solutions 
of their ores, a process too costly for general application, but 
one useful in the accurate assay of certain ores, as, for exam- 
ple, of copper ; secondly, to the copying of types, plaster 
casts, and metal-work by cathode deposits of metal ; thirdly, 
to the covering of objects made of baser metal with a thin film 
of another metal, such as gold, silver, or nickel. All these 
operations are included under the general term of electro- 
metallurgy. 

In 1836 De La Rue observed that in a Daniell's cell the 
copper deposited out of the solution upon the copper plate 
which served as a pole took the exact impress of the plate, 
even to the scratches upon it. In 1839, Jacobi, Spencer, and 
Jordan independently developed out of this fact a method of 
obtaining, by the electrolysis of copper, impressions (in 
reversed relief) of coins, stereotype plates, and ornaments. A 
further improvement, due to Murray, was the employment of 
moulds of plaster or wax, coated with a film of plumbago in 
order to provide a conducting surface upon which the deposit 
could be made. 

Electro Plating or Electro Deposition. — The full details of 
the many processes for electro plating cannot be given on 
account of their length ; the general principle includes a bat- 



NEW CATECHISM OF ELECTRICITY. 503 

ELECTROMETALLURGY. 

tery or source of electric current (say a dynamo of suitable 
size, etc., as shown and explained in connection with illustra- 
tion 288. ) 

For Rapid Boiler Repairs the electric arc is most efficient. 
It enables a patch to be applied in difficult places, Adhere riv- 
eting would be impossible without partly taking the boiler to 
pieces. For instance, parties had an upright boiler wasted by 
corrosion at one point of the outer shell. When the defect 
was cut away, there was a hole 5% in. by $% in. A piece 
of mild steel plate was cut to fit over the hole, with 1 1-2 in* 
lap all around. It was then laid in position, and the electric 
arc struck upon the junction, so as to thoroughly incorporate 
the patch with the shell. The whole job, including testing by 
hydraulic pressure, was completed in 10 hours. 

In another case, the internal bottom corners of the fire-box 
of a locomotive type boiler were badly wasted. The defects 
were repaired by building on and melting into the recesses 
small pieces of mild steel, and thoroughly incorporating the 
new pieces with the old. The leaks were stopped, and no fur- 
ther trouble experienced during eight months which have 
since elapsed. 



Note.— The extreme hardness of armor plates has one great disad- 
vantage, it is impossible to cut or drill them, and to do so is often very 
necessary, To exactly locate proposed holes, in order that they may be 
drilled before the surface of the plate is hardened, is a very expensive 
undertaking. For a long time there was no known method of drawing 
the temper from the metal in a circumscribed area, for no matter how 
heat was applied, the large mass of metal produced such rapid cooling as 
to reteraper the spot. By means of electricity, however, the problem has 
been solved, and a small section of a plate, where it is desired to drill a 
hole, may be heated to 1,000 degrees and very slowly cooled, thus drawing 
the temper satisfactorily. 



504 



NEW CATECHISM OF ELECTRICITY. 



ELECTROMETALLURGY. 
Fig. 288k 




Fig. 288 represents the operation of plating, the position of 
the anode and cathode, the battery and the bath. The battery 
has its centre or positive plate connected to a rod extending 
across the trough, to which are suspended the anodes, a y a> a> 
of gold, silver or copper, or whatever other metal from which to 
obtain a deposit. The other plates of the battery, or the nega- 
tive elements, are connected with the remaining rod across the 
trough, to which are suspended the articles to be plated, b, b> b. 

Electricity in Drilling. — The electric current is now used 
extensively to aid in drilling hardened steel. By this* meahlT 
the steel is softened in a very limited space by sending the 
current, of sufficient strength, through the metal at the 
required point. The terminal of one of the conductors is 
placed at the point where it is required to drill the hole and 
the terminal of the other conductor on the opposite side where 
the drill is intended to pass through. The application of cur- 
rent between these points will soften the metal in a direct line 
between the terminals without affecting a greater area than is 
desired. The metal being thus softened no great difficulty is 
experienced in drilling it afterward (see Note, page 503.) 



NEW CATECHISM OF ELECTRICITY. 505 

ELECTROMETALLURGY. 

Sharpening Files by Electrical Process. — The dull and 
dirty files are first placed for 12 hours iu a cold solution of 
caustic soda of 15 to 20 per cent. ; they are then cleaned with 
a scratch brush and after another immersion are again cleaned 
with a scratch brush and a 5 to 6 per cent, soda solution. 
They are then placed in the following bath : six parts nitric 
acid of 40 degrees ; 3 parts of sulphuric acid ; 100 parts of 
water. It is said to be very important to see that this bath is 
properly proportioned in order that the action is not too rapid. 
They are inserted in this bath, and connected to plates of car- 
bon immersed close to them, by means of a copper plate con- 
necting all the carbons and the files at the top. This produces 
a short-circuited battery which generates gas on the surface of 
the files. The gas formed creates bubbles which adhere to the 
points of the files, and protect them from being eaten away, 
while the rest of the file is being etched. They are taken out 
every five minutes and washed in water so as to remove the 
oxide which collects. They are then placed for half an hour 
in lime water made of one part by weight of slacked lime and 
50 parts water ; this is to remove the acid. They are then 
dried in sawdust and to prevent rusting are rubbed with a 
mixture of oil and turpentine. It is said that it requires but 
20 to 30 minutes in the electrolytic bath to sharpen the files. 



Note.— The " Elek. Zeitschrift " states that the method of sharpening 
files, described some years ago, is meeting with great favor, especially in 
England and France, where it is used very largely. Baths are in use for 
treating 300 to 400 files at a time. One workman can attend to two such 
baths. Experience has shown that one man can in this way sharpen 400 
files a day working 10 hours. The process can be repeated several times 
without injuring the files. This same method is also used to sharpen 
knives used in beet sugar factories. For this purpose it is said to give 
very good results and does not require any skilled labor, while at the same 
time it represents a considerable saving in the cost of sharpening knives. 



506 



NEW CATECHISM OF ELECTRICITY. 



Fig. 




ELECTRIC ELEVATOR, 



NEW CATECHISM OF ELECTRICITY. 507 



THE ELECTRIC ELEVATOR. 



The electric elevator — or as it is described in England, the 
Electric Lift — is a combination of the regular elevator with 
the electric motor ; i. e. y the power applied to raise and lower, 
is the electric current, as against water pressure or steam 
pressure. 

The adaptability of electricity to all service where power is 
required was never so apparent as in its application to passen- 
ger elevators ; the success of the electric hoist seems destined 
to develop a field the extent of which has not yet been calcu- 
lated. 

The essential features of the electric elevator are : (1) high 
speed, (2) absolute safety, (3) completely under control of 
operator, (4) applicable to the current to be supplied by the 
lighting mains, (5) low cost of operation and maintenance. 

In the hydraulic pumping system as well as in the hydraulic 
street pressure system, it is noteworthy that just as much 
water is required to carry up the empty car as to carry up a 
full load, and — 

If a steam pump is used it is necessary to keep the fire 
burning under the boiler and to keep the steam up all the 
time, although the pump in most cases runs only a small por- 
tion of the time, so that the consumption of coal is many 
times larger in proportion to the power used than in ordinary 
steam engines of equal power, but — 



508 NEW CATECHISM OF ELECTRICITY, 



THE ELECTRIC ELEVATOR. 

If electricity is used in connection with a proper motor, 
the consumption of current stops when the work stops, which 
insures great economy of operation whether the current sup- 
ply is obtained from a central station or from owner's dynamos. 

The advantages of the device as summarized are as follows : 

Advantages of the Electric Elevator. 

i. As compared with hydraulic elevators. 
No frozen or burst water pipes. 
No flooded cellars. 
No piston to pack and grease. 
No leaking valves or cylinders. 
No air to cause runaways. 
No excessive weight to bring car down. 
No heavy or unsightly tanks on rj^of or pressure tanks 

occupying valuable space. 
No creeping of car away from landing, if left for a few 

minutes. 
No water pipes to fill up or corrode, thereby reducing 

power and speed. 

2. As compared with steam elevators. 
No odors or heat. 
No ashes, dust, or dirt. 
No boiler insurance. 
No costly space occupied. 

No vibration of building or disagreeable noises. 
No consumption of coal while elevator is at rest. 
No waiting to get up steam. 



NEW CATECHISM OF ELECTRICITY. 



509 



Fig. 290. 




ELECTRIC elevator. 



5IO NEW CATECHISM OF ELECTRICITY. 

THE ELECTRIC ELEVATOR. 

3. General advantages. 
Prompt and easy start. 
Smooth running. 

Quick and smooth stop, regardless of load, speed, or skill. 
Requires minimum attention. 
Speed practically uniform under all loads. 
Large margin of power. 
Minimum operating expense. 

Extreme simplicity, few moving and wearing parts. 
Most approved safety devices. 

"Points" relating to the Electric Elevator: 

The satisfactory working of an electric elevator depends 
largely upon the devices by which it is started, stopped, and 
reversed ; an automatic switch and rheostat (or regulator) 
should be provided, by which these changes can always be 
made properly without strain on the apparatus, with perfect 
smoothness and without the exercise of skill on the part of the 
operator. 

Pulling the rope downwards as far as possible causes the 
car to ascend. A slight pull in the opposite direction opens 
the switch, allows the brake to apply and the car comes to a 
stop. Pulling the rope upwards as far as possible causes the 
car to descend. 

The same effect is produced by the turning of a hand 
wheel— forwards or backwards. 

Any apparatus will wear in time, and therefore elevators 
should be equipped with the most reliable and improved forms 
of safety appliances, 



NEW CATECHISM OF ELECTRICITY. 51 1 

THE ELECTRIC ELEVATOR. 

The advantages of the automatic method of control can 
hardly be overstated ; with it any person can run the elevator 
without danger of injuring the mechanism. It is impossible 
to start or stop with disagreeable suddenness. 

Car Safeties. — Bach bottom guide shoe of the cage should 
be provided with a steel safety dog with rods connecting them 
with the cables, by means of levers in the cross head, so that 
in case the lifting cables break or slacken, the dogs will throw 
in at once and lock the car to the guides. 

Slack Cable Stop. — The winding machine should be pro- 
vided with an effective device to stop the machine and prevent 
the slacking of the cables upon the drum in case the car is 
obstructed in any manner in its descent. Without such device 
the cables might become entangled with the machine and 
injured. 

Automatic Terminal Stops. — Stop balls should be securely 
fastened to the hand rope by which the switch is operated, in 
case the operator forgets or fails to pull the rope at terminal 
landings, so the car stops itself by means of these balls. 

The winding machine should be provided with a substan- 
tial and effective device that will accomplish this same result 
in case the stop balls should fail, from any cause, to do it. 

Safety Speed Governor. — The winding machine of high 
speed passenger elevators should be provided with a centrifugal 
governor, which applies a heavy auxiliary brake to the drum, 
in case of excessive speed due to any cause, bringing the whole 
apparatus to a stop. 



512 



NEW CATECHISM OF ELECTRICITY. 



Fig. 291. 




ELECTRIC ELEVATOR FOR PASSENGERS. 



NEW CATECHISM OF ELECTRICITY. 513 

THE ELECTRIC ELEVATOR. 

Safety Switch. — With some elevators if the electric current 
is interrupted by breaking of wires or by any other means 
while the motor is in operation, the car will run down too 
rapidly for safety ; a switch so constructed as to make this 
impossible should be provided. 

Electric Hoist. — A hoist does its heaviest work in starting 
its load. A steam hoist having two engines with cranks at 
right angles can only be depended upon at this time for one- 
half of its rated capacity, as one of the engines may be on a 
dead center. An electric motor, on the other hand, has no 
dead centers, and a heavy current in excess of the normal, can 
be turned into the armature for a few moments without danger. 

This important advantage is of great value, and gives elec- 
tric hoists a greater capacity, other things being equal, than a 
steam hoist. The simplicity, too, is very apparent ; instead 
of two link motions, we have a simple reversing switch, and 
the only parts subject to wear in the motor are the two bear- 
ings and the commutator. (See Fig. 108, page 235.) 

The power is transmitted to the hoist through an intermedi- 
ate gear and pinion, which is nicely covered with an iron 
guard, protecting it from dust, dirt, and liability of accidents. 
They are particularly convenient where an electric current is 
easily supplied, and very often they can be run much more 
economically than with steam. They are also very useful for 
contractors and railroad work when it is inconvenient to move 
boilers about the line. The electric wires can easily be run 
by ordinary workmen, and are always ready to tap at any 
point. 



5 M 



NEW CATECHISM OF ELECTRICITY. 



Fig. 292. 




ELECTRIC ELEVATOR WITH HOIST. 



NEW CATECHISM OF ELECTRICITY. 515 



ELECTRIC TROUBLE" OF WATCHES. 



There are two well known laws of magnetism that apply- 
to watches. 

The first is that any so-called magnetic metal, placed in the 
field of a magnet, will itself become a magnet, and will retain 
this magnetism in a more or less marked degree when removed 
from the field. Steel is an excellent example of such metals. 

The second law is that similar magnetic poles repel, and 
dissimilar poles attract, each other. By applying these laws 
we arrive at a full understanding of the effect of magnetism 
on a pocket watch of the usual construction, and an explana- 
tion of its loss of value as a timekeeper. A watch, in the field 
of a magnet strong enough to stop it, will usually, when 
removed, at once commence running again, but its time-keep- 
ing qualities will have been ruined. 

The parts affected by magnetism are the balance and 
springs. The balance in an ordinary watch moves five times 
a second ; 18,000 times an hour, and 432,000 times each day. 
But a slight change in the forces that move it are necessary to 
make a difference of several minutes each day. As the balance 
moves back and forth the magnetism of the main-spring is 
pulling or pushing it. If this force was constant and always 



5l6 NEW CATECHISM OF ELECTRICITY. 

"ELECTRIC TROUBLE" OF WATCHES. 

in the same direction the watch would run uniformly. Such, 
however, is not the case. When the main- spring is tightly- 
wound its magnetic poles are in a certain direction and in 
unwinding they are constantly changing, so that the direction 
of this force is also constantly changed. The effect on the 
balance is such as to cause the watch to run too fast sometimes 
and too slow other times. 

Non-magnetic watches are made with these parts of a non- 
magnetic metal so that they are not influenced by electric 
machinery. 

The very hard steel used for the cylinder wheel of ordinary 
watches is apt to become "highly magnetized when brought 
near dynamos running ; and this magnetization, combined 
with the earth's magnetism, always causes the watch to get 
slow, and often to stop altogether. 

In order to annihilate this magnetization, a natural magnet 
or a powerful electro-magnet must be placed in a horizontal 
position — on a table, for instance, and the watch held horizon- 
tally about half a yard off on a level with the magnet. The 
watch must then be brought slowly nearer the magnet, while 
being turned slowly, and at the same time as regularly as 
possible, between the fingers, as on a vertical axis. When the 
poles of the magnets are reached, the turning of the watch is 
to be continued, while being gradually withdrawn until the 
starting point is reached. This simple method has often been 
adopted with the desired result. 



NEW CATECHISM OF ELECTRICITY. 517 

ELECTRIC CLOCKS. 

Electric Clocks. — Electrically controlled clocks, governed 
by a standard central clock, have proved a more fruitful 
invention. In these the standard timekeeper is constructed 
so as to complete a circuit periodically, once every minute or 
half minute. The transmitted currents set in movement the 
hands of a system of dials placed at distant points, by causing 
an electromagnet placed behind each dial to attract an arma- 
ture, which, acting upon a ratchet wheel by a pawl, causes it 
to move forward through one tooth at each specified interval, 
and so carries the hands round at the same rate as those of the 
standard clock. 



TYPES OF DYNAMOS AND MOTORS- 



Scattered through this volume will be seen illustrated 
different types of dynamos and motors. The place of manu- 
facture of these various machines are given as well as — in 
some instances — of the name of the makers. 

It were vain to attempt, within the limits of this volume, 
to explain the differences, special advantages, and applications 
of each machine. 

Every reputable maker of electrical machines, and there 
are now very many such, stands back, by warranty written or 
implied, of the promised performance of his product, so each 
manufacturer is alert to improve by additions or changes his 
special designed machine. 



51 8 NEW CATECHISM OF ELECTRICITY. 



ACCIDENTS AND EMERGENCIES. 



The introduction of electricity as an industrial and useful 
agent has been attended with many distressing accidents, 
causing great suffering and frequently loss of life. 

Three instances are given of the latter to emphasize the 
necessity of constant care and skill in those in attendance on 
electrical apparatus: 

14 Charles Gruive, 30 years old, night electrical engineer of the East 
River Electric Light Company, was shocked to death at 10:30 o'clock las fc 
night in the company's plant at 425 East 24th street, New York. 

He had been standing for several minutes near one of the great 
dynamos on the second floor, when he was heard by a workman standing 
close by to utter a slight cry. He fell to the floor, and the workman, run- 
ning immediately to him, found him unconscious. Physicians from 
Bellevue Hospital tried a number of methods of resuscitation— artificial 
respiration, hypodermic injections, etc. — but to no avail. 

An examination of the body by Dr. Hoyt showed only two burus 
across the hand, so slight that they would not have been noticed in any 
other case. The face of the dead man showed no sign of pain, nor was 
any part of the body distorted. One of the workmen in the building said 
that the number of volts from the dynamos on that floor was something 
over 1,200. 

Gruive lived in Hoboken with a wife and three children, and had 
been employed for a long time by the company, being considered a care- 
ful and clever man. He went on duty at 6 o'clock last night in perfect 
health and in good spirits." 

" Louis Wentz, a press boy in the Times office, Leavenworth, Kansas, 
was instantly killed this morning by taking hold of a poorly insulated 
electric-light wire. The pressroom lights had gone out, and in attempting 
to regulate them, holding the wire in his left hand, his right hand 



NEW CATECHISM OF ELECTRICITY. 519 

ACCIDENTS AND EMERGENCIES. 

touched a screw coupling a circuit. The pressman tried to pull the boy 
away from the wire and received a shock which knocked him senseless 
for a time." 

"George Sullivan, a plumber, who was engaged in making repairs at 
the Birmingham Company's power house, Pittsburgh, Penn., was killed 
by a live wire at noon to-day. With a fellow workman he mounted a 
ladder to make a connection near the ceiling. His companion held the 
pipe, and Sullivan began to drive a nail into the wall to hold it. In strik- 
ing at the nail he missed it and struck a live wire. An awful flash 
resulted. Sullivan fell backward, striking another live wire with the 
back of his neck. He was thrown into the air, and then fell to the floor, 
dead." 

Happily, while these accidents are becoming less frequent, 
none the less it is important to both know and observe the 
rules for safety so constantly repeated. 

Reference is again particularly and emphatically made to 
the "cautions" printed under the heading of Electric Rail- 
ways, pages 441 and 447 inclusive, as well as to what follows. 

The Electric Shock. — Currents of electricity passed through 
the limbs affect the nerves with certain painful sensations, and 
cause the muscles to undergo involuntary contractions. 



Note.—' ' A rat in the City Electrical Iyight Works of Baltimore played 
havcc. He stepped from one brass terminal to another, with his front 
feet on one pole and his hind fett on the other, thus being subjected to 
2, 700 volts. In an instant there was a flash, a heavy ironstone piece of 
insulation was smashed, the net-work of wires blazed up, setting fire to 
the wooden frames of the switchboard, and hundreds of houses were 
plunged in darkness. The hair of the rat was completely burned off and 
the body became rigid as if suddenly frozen in the act of stepping across 
the terminals. Although the hair was burned off and even the skull bone 
protrnded, the body being instantly carbonized and rendered rigid, its 
attitude, when discovered, was life-like." 

" Some time ago a tame leopard escaped from its keepers at Bridgeport, 
Conn., and climbed an electric light pole and began monkeying with the 
wires. Not being posted in electric science the leopard got knocked out. 
The skin was presented to a museum." 



520 NEW CATECHISM OF ELECTRICITY. 



ACCIDENTS AND EMERGENCIES. 

The effect experienced by the discharge of electricity with 
high potential difference through the animal system is that of 
a sharp and painful shock ; pain and violent muscular con- 
traction accompany it. The voltage is the main element of 
shock, amperage has also some direct influence. 

Of currents, an alternating current is reputed worse than a 
direct current, in producing a dangerous shock. 

Electric Prostration. — The voltaic arc (arc light) is the 
source of the most intense heat and brightest light producible 
by man ; too great exposure to its rays in its more powerful 
forms causes symptoms resembling those of sunstroke. The 
skin is sometimes affected to such a degree as to come off after 
a few days. The throat, forehead and face suffer pains, and 
the eyes are irritated. These effects only follow exposure to 
very intense sources of light, or for very long times. 

The condition of the body after death by electric shock 
corresponds exactly with that found after death by asphyxia. 
The electric shock paralyzes or destroys the nerve centre 
which controls the respiratory movements ; the passage of 
venous blood into the arterial system causes contraction of 
the arterioles, and finally stoppage of the heart exactly as in 
death by drowning or suffocation. There is, therefore always 
hope of resuscitation, except when the respiratory nerve 
centre has been destroyed. M. D'Arsonval mentions a case 
in which a workman was stunned by being subjected, for a 
short time, to a pressure of 4,500 volts. About a quarter of 
an hour after the accident, assistance arrived, and artificial 



NEW CATECHISM OF ELECTRICITY. 521 

ACCIDENTS AND EMERGENCIES. 

respiration was practised. In two hours the man was able to 
speak, and finally was completely restored. 

The D'Arsonville Hethod of Resuscitation. 

The proof of the efficacy of this method is now so compler% 
that no one following electrical pursuits in which there is 
danger from electric shocks, is justified in neglecting to make 
himself familiar with it. 

First, it must be appreciated that accidental shocks seldom 
result in absolute death unless the victim is left unaided for too 
long a time, or efforts at resuscitation are suspended too early. 

In the majority of instances the shock is only sufficient to 
suspend animation temporarily, owing to the momentary and 
imperfect contact of the conductors, and also on account of 
the indifferent parts of the body submitted to the influence of 
the current. It must be appreciated also that the body under 
the conditions of accidental shocks seldom receives the full 
force of the current in the circuit, but only a shunt current, 
which may represent a very insignificant part of it. 

When an accident of this nature occurs, the following 
rules should be promptly adopted and executed with due care 
and deliberation : 

i . — Remove the body at once from the circuit by breaking 
contact with the conductors. This may be accomplished by 
using a dry stick of wood, which is a non-conductor, to roll 
the body over to one side, or to brush aside a wire, if that is 
conveying the current. When a stick is not at hand, any dry 



522 



NEW CATECHISM OF ELECTRICITY. 



Fig. 294. 



ACCIDENTS AND EMERGENCIES. 

piece of clothing may be utilized to protect the hand in seiz- 
ing the body of the victim, unless rubber gloves are conven- 
ient. If the body is in contact with the earth, the coat- tails of 

the victim, or any 
loose or detached 
piece of clothing, 
may be seized with 
impunity to draw it 
away from the con- 
ductor. When this 
has been accom- 
plished, observe 
Rule 2. 

2. — Turn the body upon the 
back, loosen the collar and cloth- 
ing about the neck, roll up a coat 
and place it under the shoulders, so 
as to throw the head back, and then 
make efforts to establish artificial 
Long Acid Glove. respiration (in other words, make 

him breathe), just as would be done in case of drowning. To 
accomplish this, kneel at the subject's head, facing him, and 
seizing both arms draw them forcibly to their full length over 
the head, so as to bring them almost together above it, and 




Note. — Linemen's rubber gloves (see illustration) are designed to 
prevent the frequent and often fatal accidents occurring to linemen from 
shock while handling electric light wires or other wires in contact with 
the same, and also the dangers of line work from lightning in stormy 
weather. The gloves are also useful in handling the strong acids of bat- 
teries, being impervious to the same. 



NEW CATECHISM OF ELECTRICITY. 523 

ACCIDENTS AND EMERGENCIES. 

hold them there for two or three seconds only. (This is to 
expand the chest and favor the entrance of air into the lungs). 
Then carry the arms down to the sides and front of the chest, 
firmly compressing the chest walls, and expel the air from the 
lungs. Repeat this manoeuvre at least sixteen times per 
minute. These efforts should be continued unremittingly for 
at least an hour, or until natural respiration is established. 

3. — At the same time that this is being done, some one 
should grasp the tongue of the subject with a handkerchief or 
piece of cloth to prevent it slipping, and draw it forcibly out 
when the arms are extended alove the head, and allow it to 
recede when the chest is compressed. This manoeuvre should 
likewise be repeated at least sixteen times per minute. This 
serves the double purpose of freeing the throat so as to permit 
air to enter the lungs, and also, by exciting a reflex irritation 
from forcible contact of the under part of the tongue against 
the lower teeth, frequently stimulates an involuntary effort at 
respiration. If the teeth are clenched and the mouth cannot 
be opened readily to secure the tongue, force it open with a 
stick, a piece of wood, or the handle of a pocket knife. 

While this is being done, a physician should be summoned. 

Electric Protector. — This is a protective device for guarding 
the human body from destructive or injurious electric shocks. 
In one system, Delany's, the wrists and ankles are encircled 
by conducting bands, which, by wires running along the arms, 
back and legs, are connected. A discharge, it is assumed, 
received by the hands will thus be short circuited around the 
body and its vital organs. 



524 NEW CATECHISM OF ELECTRICITY. 



CAUTION. 

Quotation. — " Of nearly all accidents 
arising from contact with electric wires 
and electric machines it may be said 
it is more the want of care than the 
want of knowledge." The Fig. 295 is a 
reminder of the necessity for constant 
care and watchfulness upon the part of 
all who have aught to do with electricity. 




DAXGEli SIGNAL. 



I N DEX 



Abbreviations, 114, 195. 
Accidents and Emergencies, 518. 
Accumulator, Chloride, 461. 
Adjusting lubricators, 179. 
Air Gap, Def. of, 120. 
Alphabet, Morse Telegraph, 479. 
Alternating Dynamos, 131. 

Transformer System, 359. 

Wire System (Ills.), 358. 
Alternator (Ills.), 208. 

Machine (Ills.), 314, 315. 
Alternators with Revolving Arma- 
tures, 162. 
Amber, Greek word for, 22. 
American Giant Dynamo, 188. 
Ammeter, the, 105. 

Illustration, 106. 

Station, 107. 
Ampere, the, 105 ; def., 117. 
Animal Electricity, 72. 
Anode, Def. of, 57. 
Arc Lamps, Underwriters' Rules 
Relating to, 382. 

Lighting, 345, 346; (Ills.), 98. 
Armature, 127, 128 ; (Ills.), 238. 

Bar, 143, 138. 

Core, Laminated (Ills.), 144, 145. 

Diagram of Ring, 142. 



Armature, Drum, 138. 
Ring, 138, 139. 
Faults in, 231. 
Grounds in, 241. 
Heating of, 265. 
Incorrectly placed in Chamber, 

274. 
'• Points " Relating to, 146. 
Rubbing against Pole Pieces, 291. 
Armatures, Short Circuits in, 231, 
291. 
Short Circuits between Sections 
through Frame or Core, 239. 
Thomson-Houston (Ills.)^ 139, 

141. 
Western (Complete), (Ills.), 140, 

141. 
Winding of, 296. 
Winding (Note), 307. 
Wire Wound, 143. 
Armor Plates, Electric Drilling of 

(Note), 503. 
Arresters, Lightning, Underwriters' 

Rules for, 376. 
Atmospheric Electricity, 25. 
Atom, Definition of, 42. 
Attention to Brushes, 176. 
Cutouts, 218. 



526 



NEW CATECHISM OF ELECTRICITY. 



Automatic Regulation of Dynamos, 
201. 
Switch (Ills.), 219, 226. 
Terminal Stops, 511. 

B. & S., Definition of, 229, 419. 
Ball and Wood Engine and Dyna- 
mo (Ills.), 196. 
Bar Armatures, 143. 
Bar, Digging (Ills.), 434. 
Barriett Machine (N. Y.), 268. 
Battery, Definition, 48, 498. 

Gauge, 104. 

Closed Circuit, 49, 50. 

DanielPs, 55. 

Leclanche, 53. 

Smee's, 51. 
Batteries, Bichromate, 58. 

Definitions Relating to Primary, 
47, 56. 

Electric, 51. 

Management and Care of, 59. 

Open Circuit, 49, 50. 

Storage, 457. 

Underwriters' Rules for Pri- 
mary and Storage, 400, 408. 
Bearings, Defective, 271, 275, 291. 

Heating of, 269. 

Out of Line, 275. 
Bell Circuits (Ills.), 490, 492. 

Electric, 486. 

Magneto (Ills.), 471. 

Pulls, 496. 

Telephone (Ills.), 470. 
Belt, Slack or Dirty, 291. 



Belt, Safety (Ills.), 441. 

Too Light, 270. 
Belting, 323, 325. 
Belts, Bad Joints in, 293. 
Bennett's Electroscope, 103. 
Bible, Wireman's, 373. 
Bichromate Batteries, 58. 
Binding Post (Ills.), 367. 
Bi-polar Dynamo, 125. 
Birmingham Wire Gauge, 385, 419. 
Bi-telephone, 474. 
Block and Falls with ,4 Come- 

alongs" (Ills.), 438. 
Blowpots, how to use, 435. 
Board, Switch (Ills.), 350. 
Bohenberger's Electroscope, 103. 
Boiler Repairs, Electric, 503. 
Booster, Definition of, 228. 
Boston Machine (Ills.), 245. 
Bracket, Wood (Ills.), 440. 
Brown & Sharp Wire Gauge (Ills.), 

391. 
Brush, Rockers, 171. 

Holders, 170. 
Brushes, 167, 176. 

Bad Condition of, 279, 280. 

Carbon, 168. 

Heating of, 265. 

Lead of, 169. 

44 Points" Relating to, 171. 

Strip, 168. 

Trimming, 187. 

Wheel, 169. 

Wire, 168. 
44 Bug " and ,4 Bug Trap," Def. of, 195. 



INDEX. 



527 



Bunsen Cell, 52. 
Buttons, Push, 496. 
Buzzer, Electric, 496. 

B. W. G., Definition of, 229. 

C. G. S. System of Notation, 115. 
Cable Stop, 511. 

Sub-marine (Ills.), 97. 

Supporter, 90. 
Calibration, Definition of, 118. 
Calculations of Watt Meter, 109. 
Calculations of " Power of 10," 114. 
Candle Power, 345. 
Carbon Brushes, 168. 

Telephone, 474. 
Care and Management of the Dyna- 
mo, 175, 375. 

Street Car Motor, 453. 
Car Houses (U. Rules), 400. 

Safeties, 511. 

Wiring (U. Rules), 400. 
Cathode, Definition, 57. 
Cautions for the Dynamo Room, 447. 

For Linemen, 433, 524. 
Cell, Definition of, 56, 498. 

Bunsen, 52. 

Faure, 461. 

Gravity, 54. 

Latimer Clark's Standard, 55. 

Plantes, 460. 
Centimetre-Gramme-Second Sys- 
tem, 115. 
(Central Station Testing (U. Rules), 
412. 
Chapter of u Don'ts," 276. 



Chemical Meter, 110. 
Chloride Accumulator, 461. 
Cincinnati Machine (Ills.), 240. 
Circuit Breakers (Ills.), 450. 
Circuit, Definition, 498. 

Moved so as to alter number of 
lines of force through it 
(Ills.), 68. 

Moved without cutting any lines 
of force (Ills.), 68. 
Circuits, Bell, 494, 495. 

Divided, 79. 

Lamp, 354, 355 ; (Ills.), 356. 
Circular Mil, 121. 
Clamps, Guy (Ills.), 442. 
Clark's Standard Cell, 55. 
Classification of Dynamo, 131. 
Cleat and Cover (Ills.), 409. 
Cleat, Wood (Ills.), 397. 
Climbers (Ills.), 436. 
Clocks, Electric, 517. 
Closed Circuit Battery, 49, 50. 
" Code," National, of Wiring, 373. 
Coil, Definition of, 118. 
Coils, Coupling up Field Magnet, 
259. 

Induction, 339 ; (Ills.), 340, 468. 
Collecting Brushes, 129. 
Collector, 129. 
"Come-along" (Ills.), 448. 
Commutator, 129. 

Bad Condition of, 281. 
Commutator and Brushes, Attention 

to, 185. 
Commutators, 161. 



528 



NEW CATECHISM OF ELECTRICITY. 



Commutator Lubricant, 187. 

Heating of, 265. 

Returning of, 281. 

Short Circuit in, 246. 

With Air Gap (Ills.), 162. 

Flats on, 244. 
Commuting Transformers, 339. 
Compass, Mariner's, 113. 

Needle (Note\ 100. 
Compound Dynamos in Parallel, 224. 
Compound Magnets, 34. 

Wound Dynamos, 134. 
Condensers, 339, 341 ; (Ills.), 342. 
Condensing Electroscope, 103. 
Conductivity, Testing for, 311. 
Conductors and Non-Conductors, 91. 
Conductors, Underwriters' Rules 
Relating to, 384, 405, 406, 411. 
Conduit Junction Boxes, 415. 
Conduits, Underwriters' Rules for 

Wiring, 407, 411. 
Conduits and Tubes, Note Relating 

to, 388. 
<4 Connecting Up" Dynamos, 194. 
Connections, 212, 285, 294. 
Connectors (Ills.), 418, 432. 
Consequent Pole Field Magnet, 156. 
Controllers, Railway Motor, 428. 
Converters (U. Rules), 396. 
Cooking Apparatus (U. Rules), 414. 
Cooking and Heating Electric Ap- 
paratus, 413. 
Copper (Note), 93. 

Cord, Flexible U. Rules Relating 
to, 395. 



Cores, Armature, 144. 

Counter Electromotive Force, 322. 

Coupling Compound Dynamos in 

Series, 224. 
Coupling of Dynamos, 211. 
Coupling Series Dynamos in Series, 

220. 
Coupling up Field Magnet Coils, 259. 
Crooke's Tube, 362. 
Crown of Cups (Ills.), 59. 
Cumming, Linnaeses, Quotation 

from, 16. 
Current, Electric, 22, 24, 60, 69. 

(Note), 69. 

"Points" relating to Electric, 73. 
Current Sheets, 78. 
Current, Excessive, 283. 
Currents, Eddy, 258. 
Cutouts, Automatic, 218. 

Line (Ills.), 397. 

Safety 369. 

Underwriters' Rules for, 408. 

Daniell Battery, 55. 

D'Arsonville Method of Resuscita- 
tion, 521. 

Dayton (Ohio) Machine (Ills.), 180. 

Decorative Series Lamps (U. Rule), 
396. 

Defective Bearings, 291. 

Defects of Electric Bells, 488. 

Definitions, 114, 195, 228. 

Of the National Board of F. U., 

402. 
Relating to Primary Batteries,56. 



INDEX. 



529 



Deflection, Definition of, 229, 498. 
Derivation of the word Magnet, 

(Note), 27. 
Designing a Dynamo, 252. 
Diagram of Ring Armature, 142. 
Diagram Winding (Ills.), 302, 303. 
Dialectrics, Definition of, 228. 
Diaphragm Telephone, 469. 
Direct Current Dynamos, 131. 
Direction of Iyines of Electrical 

Force, 38, 79. 
Disconnections in Armature Circuit, 

243, 286. 
Diseases of Dynamos, 260. 
Disc, Built up (Ills.), 140, 141. 
Discharge, Definition of a, 61. 
Distortion of Magnetic Field in the 

Dynamo, 256. 
Divided Circuits, 79. 
Dividing I^oad, 217. 
" Don'ts," Chapter of, 276. 
Double Field Magnet, 156. 
Double Pointed Tacks (Ills.), 409. 
Drag, Propelling, of Motors, 322. 
Drilling, Electricity in, 504. 
Drum Armature, 138. 
Drum Winding (Ills.), 296. 
Dry Cells, Definition of, 56. 
Duplex Telegraphy, 483. 
Dynamics, Definition, 23. 
Dynamic Electricity, 23, 25. 
Dynamo, Barriett, 268. 
Alternating, 131. 
American Giant, 188. 
Attention to, after it is started,182. 



Dynamo, Bi-polar, 125. 

Boston (Ills.), 245. 

Care and Management of, 175. 

Cincinnati (Ills ), 240. 

Classification of, 125, 131. 

Complete (Ills.), 130. 

Definition of, 123. 

Designing a, 252. 

Direct Current, 131. 

Distortion of Magnetic Field in 
the, 256. 

Erie (Ills.), 256. 

Farraday's, 124. 

Foundations, 173. 

Four Pole Ring (Ills.), 210. 

Four Pole with, Connections, 278. 

General Electric (Ills.), 137. 

In Action (Ills.), 126. 

Intake of a, 120. 

Model Electric lighting (Ills.), 
364. 

Multipolar, 125 ; (Ills.), 230. 

Overload of, 282, 291. 

Output of a, 120. 

Parts of, 127, 128, 129, 130. 

Parts of Arc Ivight, 288. 

Philadelphia (Ills.), 246. 

41 Points " Relating to, 172. 

Regulation for a Shunt (Ills.), 
205. 

Simplest Conceivable, 129. 

Switching a new one into Par- 
allel, 227. 

Shutting Down, 190. 

Troy, N. Y. (Ills.), 202. 



530 



NEW CATECHISM OF ELECTRICITY. 



Dynamo, Unipolar, 125. 
Dynamo-room, Instructions and 

Cautions for, 447. 
Dynamos and Motors, Types oi } 517. 

Compound in Parallel, 224. 

Compound Wound, 134. 

Connecting up, 194. 

Coupling Compound, in Series, 
224. 
Dynamos,Coupling Series, in Series, 
211, 220. 

Diseases of, 260. 

Excessive Heating of, 264. 

Regulating, 197. 

Regulating Compound, 206. 

Regulating Over Compounded, 
207. 

Regulating Series, 200. 

Reversal of Polarity of, 284. 

Separately Excited, 134. 

Series, 132. 

Series, in Parallel, 221. 

Shunt, in Series, 213. 

Shunt, in Parallel, 214. 

Shunt Wound, 133 

Starting the, 179. 

Switching into and out of Par- 
allel, 216. 
Dynamotor, 334. 

Early Experiments in Electricity,26. 

Earth Return, 498. 

"Earth, to Make," Definition, 499. 

Wire, 498. 
Eddy Currents, 258. 



Eddy Currents in Armature Cores, 
266. 

In Pole Pieces, 269. 
Edison (Bar) Armature, 138. 

Bi-polar Generator (Ills), 254. 

Conduit Junction Box (Ills.), 415. 
Edison Lamp Socket (Ills.), 352. 
Edison Meter (Ills.), 110. 
Eel, Electric (Ills.), 72. 
Efficiency, Electrical, 120. 
Electric Batteries, 51. 

Bell, 486; (Ills.), 486. 

Bells, Connecting up, 494. 

Bells, Defects of, 488. 

Clocks, 517. 

Current (Note), 60. 

Current, Experiment (Note), 74. 

Currents, Summary of Principle, 
69. 

Eel (Ills.), 72. 

Elevator, 507. 

Elevator (Ills.), 506, 509, 512 : 514. 

Energy, 42. 

Gas Lighting (U. Rules), 395. 

Heaters, Ranges and Stoves, 413. 

Hoist, 513. 

Hoisting Machine (Ills.), 235. 

Lamp (Ills.), 253. 

Lighting, 345. 

Lights and Motors in General 
Storage Stores, 412. 

Light Plant Str. "Bay State," 
344. 

Locomotive, 431. 

Locomotive, Economy of, 332. 



INDEX. 



531 



Electric Power Transmission, 326, 
(Note) 327. 

Power Transmission for I/mg 
Distances, 331. 

Prostration, 520. 

Protector, 523. 

Pumps, 500. 

Pump and Automatic Tank 
Switch (Ills.), 501. 

Railway, 422. 

Shock, 519. 

Trouble of Watches, 515. 
Electrical Battery, Action of, 50. 

Efficiency, Definition of, 120. 

Machine, Indianapolis(llls.), 122. 

Measurements, 99. 

Resistance, 87. 
Electricity and Magnetism, Differ- 
ence between, 43. 
Electricity, Definition, 16, 22, 25. 

Definition of (Note), 43. 

Animal, 72. 

Atmospheric, 25. 

Current, 22, 24. 

Derivation of Name (Note), 22. 

Dynamic, 23. 

Early Experiments in, 26. 

Frictional, 25. 

In Drilling, 504. 

In Rotation, 22. 

In Vibration, 22, 24. 

Magneto, 25. 

Negative, 23, 24. 

Positive, 23, 24. 

Resinous, 25. 



Electricity, Static, 22, 23. 

Vitreous, 25. 

Voltaic, 25. 
Electrodes, Definition of, 56. 
Electrolysis, Definition of, 58. 
Electrolyte, Definition of, 57. 
Electro Magnets (Note), 40; (Ills.), 
76. 

Ammeters, 105. 

Magnetic Induction, 83. 

Magnetism, 35. 

Meter, 103. 
Electrometallurgy, 502. 
Electro-Motive Force, 45. 

Counter, 322. 
Electron, Definition, 22. 
Electro Plating, 504. 
Electro Statics, 23. 
Electroscope, 103. 
Elements, Separating the, 58. 
Elevator, Electric, 507. 

Advantages of, 508. 

Electric (Ills.), 506, 509, 512, 514. 

"Points " Relating to, 510. 
E. M. F., Definition of, 114. 
Emergencies and Accidents, 518. 
Energy, Definition of, 42. 

Electric, 42. 

Kinetic, Potential, Static (Note), 
44. 
Equalizing I^oad, 227. 
Exciting Fluid, 57. 
Exchange, Telephone, 474. 

F., Meaning of, 229. 



532 



NEW CATECHISM OF ELECTRICITY. 



Failure to Excite, 261. 
Fa rra day's Discovery, 63. 

Dynamo (Ills.), 124. 
Faults in Armatures, 231. 
Telegraph Lines, 484. 
Faure Cell, 461. 
Feeder Line " Ears " (Ills.), 444. 

Wires, 455. 
Field Magnets, 127, 129, 150 ; (Ills.), 
153. 
Heating of, 266. 
Rule for Connecting up, 193. 
Field Magnet Windings, 301. 
Field, Magnetic, 31, 32. 
Files, Sharpening by Electrical 

Process, 505 ; (Note), 505. 
Fixture Work, Underwriter's Rules, 

393. 
Flashing or Sparking, 277. 
Flats on Commutator, 244. 
Flemming's Rule, 80. 
Flow of Water under Pressure or 

Head (Ills), 126. 
Flux, Magnetic, 31. 
Force, Direction of Lines of Elec- 
trical, 79. 
Direction of Magnetic, 38. 
Electro-Motive, 45. 
Lines of Magnetic, 37. 
Foucault Currents, Definition of, 

229. 
Foundations for Trolley Pole, 421. 

Of Dynamos, 173. 
Four Pole Dynamo with Connec- 
tions, 278. 



Franklin's Experiment (Note), 24. 
Frictional Electricity, 25. 
Frog's Leg, Discovery, 61. 
Function, Definition of, 115. 
Fuse and Connections (Ills.), 454. 

Blocks, 369. 
Fuses, 369. 

"Points" Relating to Safety, 
371. 

Safety (U. Rules), 390; (Ills.), 370. 

Galvaniscope, 102. 
Galvani's Discovery,[61. 
Galvanism, 61. 
Galvanometer, 101-103. 
Gauge, Battery, 104. 

Brown & Sharpe Wire (Ills.), 391. 

Birmingham Wire (Ills), 385. 

Micrometer Wire (Ills.), 379. 

Standard Wire, (Ills.), 391. 
Gauges, Wire, 419. 
Geisler Tube, 361. 

General Electric Dynamo (Ills.), 137. 
Generator, Edison Bi-polar (Ills.), 
254. 

List of Parts of Edison Bi-polar 
(Ills.), 255. 
Generators, Motor, 339. 

Rules for, 375. 
Glass Insulator (Ills.), 446. 
Globe Insulator (Ills ), 440. 
Glove, Safety (Ills.), 522. 
Glue-pots, Electric, Underwriters' 

Rules Relating to, 414. 
Gold Leaf Electroscope, 103. 



INDEX. 



533 



Governor, Safety Speed Elevator, 511. 
Gravity Ammeters, 105. 

Cells, 54. 
Grounds in Armature, 241. 
Guy Clamp (Ills.), 442. 

Hanger and Ear (Ills.), 146. 

Barn or Bridge (Ills.), 454. 
Heat, Conduction from Armature, 

275. 
Heating and Cooking Apparatus, 

Electric (U. Rules), 413. 
Heating of Armature, Commutator, 
and Brushes, 265. 

Of Bearings, 269. 

Of Connections, 264. 

Of Dynamos, 264. 

Of Field Magnets, 266. 
Hoist, Electric, 513. 
Holders, Brush, 170. 
Horseshoe Magnet, 34. 
Houses, Car (U. Rules), 406. 
How to Use the Telephone, 472. 

Incandescent Lamps in Series Cir- 
cuit (U. Rules), 383. 

Lighting, 345, 353. 
Index Notation, 114. 
Induction Coil (Ills.), 340, 471. 

Coils, 339, 343, 468. 

Electric Magnetic, 83. 
Inertia, 114. 

Inside Wiring (Ills.), 409. 
Instructions and Cautions for the 
Dynamo Room, 447. 



Instructions and Cautions for Line- 
men, 433, 441. 
Insulated Wire (Ills.), 471. 
Insulation, Testing for, 311, 313. 
Insulator, Glass (Ills.), 446. 

Globe Strain (Ills ), 89. 

Rubber Hook, 450. 
Insulators (Ills.), 440. 

Porcelain (Ills.), 397. 

Tree (Ills.), 444. 
44 Intake" of a Dynamo, 120. 
Introduction, 15. 
Inversely, Definition of, 119. 

Joints, Direction for Making Good, 
493. 
Making, 433. 
Journals, Too Tight, 270 ; Badly Fit- 
ted, 272. 

Kathode (or Cathode), Definition of, 

57. 
Key and Relay, Telegraph (Ills.), 
481. 
Board (Ills ), 481. 
Transmitting Telegraph, 476. 
Kilo Watt, Definition of, 121. 
Kinetic Energy (Note), 44. 
Knife Switches, 348. 

Lag, Magnetic, 31. 
Laminated Armature Core (Ills.), 
145. 
Definition of, 118. 
Lamps, Arc (U. Rule), 405. 



534 



NEW CATECHISM OF ELECTRICITY. 



Lamp Circuits, 354, 355 ; (Ills.), 356. 

Decorative Series (XL Rule), 396. 

Electric, of the Future, 360. 

Electric (Ills.), 253, 363. 

Standard Incandescent, "62. 
Lamp Sockets, 350 ; (Ills.), 352. 
Lap Winding, 306; (Ills.), 308. 
Laws of Klectrical Resistance, 88. 
Lead of Brushes, 169. 
Leclanche Battery, 53. 
Lifting Power of Magnets (Ills.), 46. 
Lightning Arresters, U. Rules for, 

376. 
Lighting, Electric, 345. 

Electric (Note), Curious Re- 
marks, 349. 
Line Appliances, 442, 444. 

Battery, 499. 

Cutout (Ills.), 397. 
Lines of Magnetic Force, 37. 
Line Work, 433. 
Lineman's Pliers (Ills.), 436. 

"Climbers" (Ills ), 436. 

Construction Tools, 432, 434, 436, 
438, 440. 

Safety Belt (Ills.), 441. 
Linemen, Instructions and Cautions 

for, 433. 
Load, Equalizing, 227. 
Local Action, Definition of, 57. 

Battery, 499. 
Locomotive, Electric, 431. 

Electric, Economy of, 332. 
Long Distance Telephone Trans- 
mitter (Ills.), 468. 



Lubricant on Commutator, 187. 
Lubrication, Defective, 270. 
Lubrications, Adjusting, 179. 

Machine, Dayton, Ohio (Ills.), 180. 

Eau Claire, Mo. (Ills.), 166. 

Electric Hoisting, 235. 

Siemens-Halske (Ills.), 160. 

Westinghouse (Ills.), 149. 

Windsor (Conn.), 174. 
Magnet, Artificial, 34. 

Bar (Ills.), 76 

Consequent Pole Field, 156. 

Derivation of the word (Note), 27. 

Double Field, 156. 

Horseshoe, 34. 

Multipolar Field, 158. 

Natural, 34. 

Overtype Field (Ills.), 154. • 

Polarized Electro, 34. 

" Relay," 483. 

Salient Pole Field (Ills.), 153. 

Strength of, 33. 

Typical Field (Ills.), 153. 

Undertype Field (Ills.), 155. 
Magnetic and Electric Current, 60. 

Field, 31, 32. 

Flux, 31. 

Lag, 31. 

Permeability, 119. 

Saturation, 31. 

" Tick, "32. 

Whirl (Ills.), 66. 
Magnetism and Magnets, 27. 

Definition, 22. 



INDEX. 



535 



Magnetism, Electro, 35. 

Residual, 31. 
Magneto Bell (Ills.), 471. 

Bell and Generator (Ills.), 490. 

Electricity, 25. 

Testing Instrument (Ills.), 473. 
Magnets and Magnetism, 27. 
Magnets, Compound, 34 

Lifting Power of (Ills.), 46. 

11 Points" Relating to Electro, 39. 

Useful Definitions Relating to,34. 
"Make and Break," Definition of, 

229. 
Management and Care of Batteries, 

59. 
Mariner's Compass, 113. 
Matter, Definition of, 42. 
Maycock, W. Perrin, Quotation 

from, 17. 
Mclntire Sleeve and Joint (Ills.), 118. 

Splicing Tool (Ills.), 438. 
Measurements, Electrical, 99. 
Measurement, Method of, 248. 
Measurement of Electric Pressure, 
105. 

Current Volume, 105. 
Measurements of Resistance, 112. 
Mechanical Clip (Ills.), 454. 
Meter, Chemical, 110. 

Edison (Ills.), 110,111. 

Station, 109. 

Watt, 109. 
Method of Measurement, 248. 
Micrometer Wire Gauge, 419 ; (Ills.), 
379. 



Mil, Definition of, 121. 

Circular, 121. 
Mines, Electrical Transmission in, 

330. 
Mirror, Galvanometer, 103. 
Molecule, Definition of, 42. 
Monocyclic System, 318, 319. 
Morse Key (Ills.), 481. 

Telegraph Alphabet, 479. 
Motor, Care and Management of the 

Street Car, 453. 
Motor-Generators, 339. 
Motor, Street Car (Ills.), 427. 
Motors, 320, 426 ; (Ills.), 321. 

Alternating Current, 320. 

Continuous Current, 320. 

In Storage Houses (U. Rule), 412. 

Propelling Drag of, 322. 

Types of Dynamos and, 517. 

Regulation of, 209. 

Underwriters' Rules for Wiring, 
etc., 377. 
Mouldings Underwriters' Rules Re- 
lating to, 388. 
Mouth Piece, Telephone (Ills.), 468. 
Multiphase Currents, 317. 
Multipolar Field Magnets, 158. 

Dynamo (Ills.), 230. 

Dynamo, 125. 
Multiple Series System, 357. 

Arc System, 357. 

National Board Fire Underwriters' 
Rules, 374. 
Code of Wiring, 373. 



536 



NEW CATECHISM OF ELECTRICITY. 



Natural Magnet, 34. 

Needle, Compass (Note), 100. 

Negative Electricity, 23. 
Energy, 45. 

New York Board of Fire Underwrit- 
ers Addenda to other Rules, 
411. 

Niagara Falls Electric Power, 333. 

Non-Conductors and Conductors, 91. 

Ohm, the, 105. 

Definition of, 116. 
Ohm's Law, 116. 
Open Circuit Batteries, 49, 50. 
" Output" of a Dynamo, 120. 
Overhead Transmission (Ills.), 425. 
Overload of Dynamo, 282, 291. 
Overtype Field Magnet (Ills.), 154. 

Parts of Arc Light Generator, 288. 

Of Dynamo, 127-130. 

Of Edison Bipolar Generator, 
(Ills.), 255. 
Periodicity, Definition of, 119. 
Periphery, Definition of, 118. 
Permanent Magnet Ammeters, 105. 
Permeability, 119. 
Pith Ball Electroscope, 103. 
Plante's Cell, 460. 
Plug, Insulated (Ills.), 440. 
" Points " Relating to the Armature, 
146. 

Relating to Brushes, 171. 

Relating to the Commutator, 
163-165. 



" Points " Relating to the Dynamo, 
172. 

Relating to Electric Current, 13. 

Relating to Electric Elevator, 
510. 

Relating to Electro-Magnets, 39. 

Relating to Safety Fuse, 371. 
Polarity, Definition of, 119. 
Polarization, Definition of. 57. 
Polarized Electro Magnet, 34. 
Poles, Definition of, 57. 
Pole Pieces, 129. 

Ratchet (Ills.), 432. 

Support (Ills.), 432. 
Positive Electricity, 23. 

Energy, 45. 
Potential, Definition of, 118. 

Energy (Note), 44. 
Power, Candle, 345. 
Powers of Ten, 114. 
Practical Operation of the Tele- 
phone, 470. 
Preface, 11. 

Press Buttons (Ills ), 498. 
Pressure, Electrical, Unit of, 105. 
Primary Batteries, 47. 
Propelling Drag of Motors, 322. 
Prostration, Electric, 520. 
Protector, Electric, 523. 
Protectors, U. Rule for Wire, 410. 
Pull-off and Ear (Ills.), 456. 
Pulls, Electric Door, 496. 
Pumps, Electric, 500; (Ills.), 501. 
Push Buttons, 496. 



537 



Quadrant Electrometer, 103. 

Electroscope (Henly), 102. 
Quotation Relating to Danger, 524. 

Rail Joints (Ills.), 442. 
Railway, Electric, 422. 

Motor Controllers, 428; (Ills.), 
429. 
Ratchet, Pole (Ills.), 432. 
Receiver, Telephone, 469 ; (Ills.), 468. 
Reel and Stand (Ills.), 438. 
Regulating Compound Dynamos, 
206. 

Dynamos, 197. 

Series Dynamos, 200. 
Regulation for a Shunt Dynamo 
(Ills.), 205. 

Of Dynamos, Automatic, 201. 

Of Motors, 209. 
Relay, Telegraph, 483. 
Reluctance, Definition of, 118. 
Repair Shop, 452. 
Residual Magnetism, 31. 
Resinous Electricity, 25. 
Resistance Boxes, Definition of, 404. 
Resistance Boxes and Equalizers, 

Underwriters' Rules, 376. 
Resistance, Electrical, 87. 

Electrical, Unit of, 105. 

Water (Ills.), 342. 
Resuscitation, D'Arsonville Method 

of, 521. 
Reversal of Polarity of Dynamos, 284. 
Rheostat and Armature (Ills.), 242, 
348. 



Ring Armature, 138, 139. 

Ring Windings, 301 ; (Ills.), 296. 

Rockers, Brush, 171. 

Rosette, Porcelain (Ills.), 367. 

Rowland, Prof., Quotation from, 17. 

Rubber Hook Insulator (Ills.), 450. 

Tubing (Ills.), 403. 
Ruhmkorff Coil (Ills.), 340, 343. 
Rule, Flemming's (Ills.), 81. 
Rule for Coupling up Field Magnet 

Coils, 193. 
Rules and Fecommendationsof Fire 
Underwriters, 374. 

Sad-Irons, Electric, etc , U. Rules 
Relating to, 416. 

"Safeties," Car, 511. 

Safety Belt (Ills.), 441. 
Catches, 369. 

Fuses, Underwriters' Rules Re- 
lating to, 390 ; (Ills.), 370. 
Speed Elevator Governor, 511. 
Switch, 513. 

Salient Pole Field Magnet (Ills.), 
153, 154. 

Saturation, Magnetic, 31. 

Sawyer-Mann I,amp Socket (Ills.), 
352. 

Secondary Batteries (Note), 48. 

Segments, Loose or Knocked in, 247. 

Separately Exciter! Dynamos, 134. 

Series and Parallel Connections, 
212. 

Series Dynamos, 132, 221. 

Service Blocks (U. Rules), 380. 



538 



NEW CATECHISM OF ELECTRICITY. 



Shafting, Bent or Badly Turned, 272. 

End Pressure of, 273. 
Sheets, Current, 78. 
Shock, Electric, 519. 
Short Circuits between Adjacent 

Coils, 236. 
. In Armatures, 231, 239, 291. 

In Armature Circuit, 286. 

In Commutator, 246. 

Or Disconnections in Armature 
Circuits, etc., 293. 

In Coils, 232. 
Shunt, Definition of, 118. 

Dynamos in Parallel, 214. 

Dynamos in Series, 213. 

Wound Dynamos, 133. 
Shutting Down Dynamo, 190. 
Siemens Armature, 139. 
Siemens-Halske Machine (Ills.), 160. 
Sleeve, 418. 
Smee's Battery, 51. 
Sockets, Electric Lamp, Underwrit- 
ers' Rules Relating to, 395. 

Lamp, 350. 
Solenoids, 77. 

Sparking or Flashing, 277. 
Speed of Electric Current (Note), 74. 
Speed, Reduced, of Driving Engine, 
290. 

Irregularities of, 290, 292. 
Splicing Tool (Ills.), 438. 
Spring Ammeters, 105. 
Staggering, Definition of, 119. 
Standard Wire Gauge (Ills.), 391. 
Starting Dynamos, 179. 



Static Electricity, 22, 23. 

Energy (Note), 44. 
Station Ammeter, 107. 

Meter, 109. 
Station, U. Rules for Power, 408. 
Steamer " Bay State " Electric Light 

Plant, 344. 
Stoletow, A., Quotation from, 17. 
"Stop," Slack Cable, 511. 
Stops, Automatic Terminal, 511. 
Storage Batteries, 338, 457; (Ills.),462. 
Storage Batteries (Note) 460. 
Storage or Primary Batteries (U. 

Rules\ 400. 
Street Car Motor (Ills.), 427 
Strength of a Magnet, 33. 
Submarine Telegraph, 485. 
Supporter, Cable, 90. 
Surface System, Electric Railway f 

424. 
Switch (Ills.), 471. 

Automatic (Ills ), 219, 226. 

Automatic Tank and Electric 
Pump (Ills.), 501. 

Safety Elevator, 513. 
Switchboard, 359, 474. 
Switchboards, 404 ; (Ills.), 350. 

Underwriters' Rules for, 376. 
Switches (Ills.), 348. 

Underwriters' Rules Relating to, 
392. 
Switching a New Machine into 
Parallel, 227. 

Dynamos Into and Out of Par- 
allel, 216. 



539 



Symbols, Abbreviations and Defini- 
tions, 114, 195, 228. 
Synchronous, Definition of, 195. 
System, Alternating Transformer, 
359. 
Multiple Arc, 357. 
Multiple Series, 357. 
Surface Electric Railway, 424. 
Three-wire, 357. 
Underground Electric Railway, 

424. 
Of Lamp Distribution, 357. 

Table of Capacity of Wires, 390. 
Table Showing the Relative Dimen- 
sions of Pure Copper Wire, 
464. 
Tacks, Double Pointed (Ills.), 409. 
Tamping Bar (Ills.), 434. 
Telegraph Lines, Faults in, 484. 
Telegraph, 476, 477. 

Submarine, 485. 
Telegraphy, Duplex, 483. 
Telephone, 466. 

Bell (Ills.), 470. 

Bi-, 474. 

Carbon, 474. 

Exchange, 474; (Note), 474. 

How to Use the 472. 

Practical Operation of the, 470. 

N. Y. System (Note), 469. 
Terminals (Ills ), 442. 
Testing Central Stations, U.Rule,412. 

Circuits, Underwriters' Rule for, 
377. 



Testing for Conductivity, 311. 

For Insulation, 311. 
Thomson-Houston Arc Light Gen- 
erator (Ills.), 289. 

Armature (Ills.), 139. 

Lamp Socket (Ills.), 352. 
Thompson, S. P., Quotation from, 16. 
Three-wire Incandescent System, 

(Ills.), 358. 
Three-wire System, 357. 
Tick, Magnetic, 32. 
Tools, Care of (Ills.), 452. 

Linemen's Construction, 432, 
434, 436, 438, 440. 

List of, for Small Inside Wiring, 
368. 
Torque, Definition of, 120. 
Tower Wagon (Ills.), 86. 
Transformer, Operation of, 337. 
Transformers, 335. 

Commuting, 339. 
Transmission (Electric), in Mines, 
307. 

Overhead (Ills.), 425. 

Power, 326. 
Transmitter and Receiver (Ills.), 
468. 

Telephone, 469. 
Transmitting Key (Ills.), 476. 
Tree Insulators (Ills.), 444. 
Trimming Brushes, 187. 
Trolley Cross Over (Ills.), 454. 

Car (Ills), 420. 

Frog (Ills.), 440. 

Wheel 424 ; (Ills.), 448. 



540 



NEW CATECHISM OF ELECTRICITY. 



Trolley Wire, Pole, Connections and 
Foundations (Ills ), 421. 
Wire, Location of, 452. 
Wires (U. Rules), 399 
Tubing, Rubber (Ills.), 403. 
Twophase Current, 317. 
Two- Wire Incandescent System, 

(Ills.), 358. 
Types of Dynamos and Motors, 517. 

Underground System, Electric Rail- 
way, 424. 
Undertype Field Magnet (Ills.), 155. 
Underwriters' Rules and Recom- 
mendations, 374, 384. 
Relating to the Alternating Sys- 
tem, 396. 
Electric Power Stations, 399. 
High Potential System, 378. 
Low Potential Systems, 383. 
Wiring in Special Places, 388. 
For Outside Wiring, 386. 
Unipolar Dynamo, 125. 
Unit of Pressure, 105. 
Of Rate of Flow, 105. 
Of Resistance, 105. 
Useful Definitions Relating to Mag- 
nets, 34. 

Vacuum Tube Electric Lamps, 360. 
Variation of Speed, 290. 
Vibrating Electric Bells, 488. 
Vibration, 295. 

Electricity in, 22, 24. 
Vitreous Electricity, 25. 



Volt, the, 105, 117. 
Voltaic Electricity, 25. 
Voltage, Excessive, 283, 292. 
Voltaic Cell, Definition of, 56. 
Volta's Discovery, 62. 
Voltmeter, 108 ; (Ills.), 106. 

Watches, Electric Trouble of, 515. 
Water, Illustration of Flow, 126. 

Resistance (Ills.), 342 

Meter for Power Stations (Ills.), 
194. 
Watt, Definition of, 121. 

Meter, 109 ; (Ills.), 109. 
Wave Winding, 306 ; (Ills.), 309, 310. 
Western Armature (Ills ) , 140, 141. 
Western Union Wire Joint (Ills.), 

418. 
Westinghouse Machine (Ills.), 149. 
Wheel, Trolley, 424. 

Brushes, 169. 
Winding Armature (Note), 307. 

Diagram (Ills.), 302, 303. 

Drum (Ills.), 296. 

For Four Pole Machine (Ills.), 
304, 305. 

For Separately Excited Dynamo 
(Ills.), 136. 

L-ap, 306; (Ills.), 308. 

Machine (Ills.), 454. 

Of Armatures, 296. 

Ring, 301 ; (Ills.), 296. 

Wave, 306 ; (Ills.), 309, 310. 
Windings, Field Magnet, 301. 
Wire, Covered (Ills.), 409, 471, 342. 



541 



Wire, Direction for Making Good 

Joints, 493. 

Cutters (Ills.). 434. 
Gauges, 419. 

Protectors, U. Rule for, 410. 
Table Showing the Relative Di- 
mensions of Pure Copper 
Wire, 464. 
Ties (Ills.), 456. 
Wire Wound Armatures, 143. 
Wireman's Bible, 373. 
Wires, Feeder, 455. 

Ground Return (U. Rules), 400. 



Table of Capacity, 390. 

Trolley, Underwriters' Rules 

Relating to, 399. 
Wiring, 365. 

Car (U. Rules), 400. 

Inside (Ills.), 409. 

Rules and Requirements, 375. 

Underwriters' Rules for Special, 

407. 

Wood Bracket (Ills.), 440. 

Cleat (Ills.), 397. 

Pin (Ills.), 440. 



Fig. 



/HAWKAN'SV, 

;:;;i:...:,^..,.,-':;.-- v ---' '■' 




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